diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7c5deea..f2ecc17 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 0.3.0-nullsafety.0
+
+* Migrate to null safety
+* Fix unknown config parameters causing a crash and add related warnings
+
 ## 0.2.0
 
 * **IMPORTANT:** 'CFF' table is generated now instead of 'CFF2'.
diff --git a/bin/fontify.dart b/bin/fontify.dart
index 92bae45..d67f8e2 100644
--- a/bin/fontify.dart
+++ b/bin/fontify.dart
@@ -14,7 +14,7 @@ final _argParser = ArgParser(allowTrailingOptions: true);
 void main(List<String> args) {
   defineOptions(_argParser);
 
-  CliArguments parsedArgs;
+  late final CliArguments parsedArgs;
 
   try {
     parsedArgs = parseArgsAndConfig(_argParser, args);
@@ -29,7 +29,7 @@ void main(List<String> args) {
 
   try {
     _run(parsedArgs);
-  } on dynamic catch (e) {
+  } on Object catch (e) {
     logger.e(e.toString());
     exit(65);
   }
@@ -47,11 +47,11 @@ void _run(CliArguments parsedArgs) {
 
   if (parsedArgs.classFile?.existsSync() ?? false) {
     logger.v(
-        'Output file for a Flutter class already exists (${parsedArgs.classFile.path}) - '
+        'Output file for a Flutter class already exists (${parsedArgs.classFile!.path}) - '
         'overwriting it');
   }
 
-  if (parsedArgs.fontFile?.existsSync() ?? false) {
+  if (!parsedArgs.fontFile.existsSync()) {
     logger.v(
         'Output file for a font file already exists (${parsedArgs.fontFile.path}) - '
         'overwriting it');
@@ -96,7 +96,7 @@ void _run(CliArguments parsedArgs) {
       package: parsedArgs.fontPackage,
     );
 
-    parsedArgs.classFile.writeAsStringSync(classString);
+    parsedArgs.classFile!.writeAsStringSync(classString);
   }
 
   logger.i('Generated in ${stopwatch.elapsedMilliseconds}ms');
@@ -112,7 +112,7 @@ void _usageError(String error) {
   exit(64);
 }
 
-void _printUsage([String error]) {
+void _printUsage([String? error]) {
   final message = error ?? _kAbout;
 
   stdout.write('''
diff --git a/lib/src/cli/arguments.dart b/lib/src/cli/arguments.dart
index 1977306..75af690 100644
--- a/lib/src/cli/arguments.dart
+++ b/lib/src/cli/arguments.dart
@@ -121,7 +121,7 @@ class CliArguments {
   ///
   /// Throws [CliArgumentException], if there is an error in arg parsing
   /// or if argument has wrong type.
-  factory CliArguments.fromMap(Map<CliArgument, Object> rawArgMap) {
+  factory CliArguments.fromMap(Map<CliArgument, dynamic> rawArgMap) {
     // Validating types
     for (final e in _kArgAllowedTypes.entries) {
       final arg = e.key;
@@ -136,58 +136,36 @@ class CliArguments {
     }
 
     final map = formatArguments(rawArgMap);
+    _validate(map);
 
     return CliArguments(
       map[CliArgument.svgDir] as Directory,
       map[CliArgument.fontFile] as File,
-      map[CliArgument.classFile] as File,
-      map[CliArgument.className] as String,
-      map[CliArgument.indent] as int,
-      map[CliArgument.fontPackage] as String,
-      map[CliArgument.fontName] as String,
-      map[CliArgument.recursive] as bool,
-      map[CliArgument.ignoreShapes] as bool,
-      map[CliArgument.normalize] as bool,
-      map[CliArgument.verbose] as bool,
-      map[CliArgument.configFile] as File,
+      map[CliArgument.classFile] as File?,
+      map[CliArgument.className] as String?,
+      map[CliArgument.indent] as int?,
+      map[CliArgument.fontPackage] as String?,
+      map[CliArgument.fontName] as String?,
+      map[CliArgument.recursive] as bool?,
+      map[CliArgument.ignoreShapes] as bool?,
+      map[CliArgument.normalize] as bool?,
+      map[CliArgument.verbose] as bool?,
+      map[CliArgument.configFile] as File?,
     );
   }
 
   final Directory svgDir;
   final File fontFile;
-  final File classFile;
-  final String className;
-  final String fontPackage;
-  final int indent;
-  final String fontName;
-  final bool recursive;
-  final bool ignoreShapes;
-  final bool normalize;
-  final bool verbose;
-  final File configFile;
-
-  /// Validates CLI arguments.
-  ///
-  /// Throws [CliArgumentException], if argument is not valid.
-  void validate() {
-    if (svgDir == null) {
-      throw CliArgumentException('The input directory is not specified.');
-    }
-
-    if (fontFile == null) {
-      throw CliArgumentException('The output font file is not specified.');
-    }
-
-    if (svgDir.statSync().type != FileSystemEntityType.directory) {
-      throw CliArgumentException(
-          "The input directory is not a directory or it doesn't exist.");
-    }
-
-    if (indent != null && indent < 0) {
-      throw CliArgumentException(
-          'indent must be a non-negative integer, was $indent.');
-    }
-  }
+  final File? classFile;
+  final String? className;
+  final String? fontPackage;
+  final int? indent;
+  final String? fontName;
+  final bool? recursive;
+  final bool? ignoreShapes;
+  final bool? normalize;
+  final bool? verbose;
+  final File? configFile;
 }
 
 /// Parses argument list.
@@ -196,7 +174,7 @@ class CliArguments {
 ///
 /// Returns an instance of [CliArguments] containing all parsed data.
 CliArguments parseArguments(ArgParser argParser, List<String> args) {
-  ArgResults argResults;
+  late final ArgResults argResults;
   try {
     argResults = argParser.parse(args);
   } on FormatException catch (err) {
@@ -210,7 +188,7 @@ CliArguments parseArguments(ArgParser argParser, List<String> args) {
   final posArgsLength =
       math.min(_kPositionalArguments.length, argResults.rest.length);
 
-  final rawArgMap = <CliArgument, Object>{
+  final rawArgMap = <CliArgument, dynamic>{
     for (final e in kOptionNames.entries) e.key: argResults[e.value],
     for (var i = 0; i < posArgsLength; i++)
       _kPositionalArguments[i]: argResults.rest[i],
@@ -219,30 +197,48 @@ CliArguments parseArguments(ArgParser argParser, List<String> args) {
   return CliArguments.fromMap(rawArgMap);
 }
 
+MapEntry<CliArgument, dynamic>? _mapConfigKeyEntry(
+  MapEntry<dynamic, dynamic> e,
+) {
+  final dynamic rawKey = e.key;
+  void logUnknown() => logger.w('Unknown config parameter "$rawKey"');
+
+  if (rawKey is! String) {
+    logUnknown();
+    return null;
+  }
+
+  final key = kConfigKeys.getKeyForValue(rawKey);
+  if (key == null) {
+    logUnknown();
+    return null;
+  }
+
+  return MapEntry<CliArgument, dynamic>(key, e.value);
+}
+
 /// Parses config file.
 ///
 /// Returns an instance of [CliArguments] containing all parsed data or null,
 /// if 'fontify' key is not present in config file.
-CliArguments parseConfig(String config) {
-  final Object parsedYaml = loadYaml(config);
+CliArguments? parseConfig(String config) {
+  final dynamic yamlMap = loadYaml(config);
 
-  if (parsedYaml is! YamlMap) {
+  if (yamlMap is! YamlMap) {
     return null;
   }
 
-  final yamlMap = parsedYaml as YamlMap;
-  final Object fontifyYaml = yamlMap['fontify'];
+  final dynamic fontifyYamlMap = yamlMap['fontify'];
 
-  if (fontifyYaml is! YamlMap) {
+  if (fontifyYamlMap is! YamlMap) {
     return null;
   }
 
-  final fontifyYamlMap = fontifyYaml as YamlMap;
+  final entries = fontifyYamlMap.entries
+      .map(_mapConfigKeyEntry)
+      .whereType<MapEntry<CliArgument, dynamic>>();
 
-  final argMap = <CliArgument, Object>{
-    for (final e in fontifyYamlMap.entries)
-      if (e.key is String) kConfigKeys.getKeyForValue(e.key as String): e.value,
-  };
+  final argMap = Map<CliArgument, dynamic>.fromEntries(entries);
 
   return CliArguments.fromMap(argMap);
 }
@@ -259,7 +255,7 @@ CliArguments parseArgsAndConfig(ArgParser argParser, List<String> args) {
   final configList = [parsedArgs.configFile, ...defaultConfigList];
 
   for (final configFile in configList) {
-    if (configFile?.existsSync() ?? false) {
+    if (configFile != null && configFile.existsSync()) {
       final parsedConfig = parseConfig(configFile.readAsStringSync());
 
       if (parsedConfig != null) {
@@ -270,10 +266,36 @@ CliArguments parseArgsAndConfig(ArgParser argParser, List<String> args) {
     }
   }
 
-  parsedArgs.validate();
   return parsedArgs;
 }
 
+/// Validates CLI arguments.
+///
+/// Throws [CliArgumentException], if argument is not valid.
+void _validate(Map<CliArgument, dynamic> args) {
+  final svgDir = args[CliArgument.svgDir] as Directory?;
+  final fontFile = args[CliArgument.fontFile] as File?;
+  final indent = args[CliArgument.indent] as int?;
+
+  if (svgDir == null) {
+    throw CliArgumentException('The input directory is not specified.');
+  }
+
+  if (fontFile == null) {
+    throw CliArgumentException('The output font file is not specified.');
+  }
+
+  if (svgDir.statSync().type != FileSystemEntityType.directory) {
+    throw CliArgumentException(
+        "The input directory is not a directory or it doesn't exist.");
+  }
+
+  if (indent != null && indent < 0) {
+    throw CliArgumentException(
+        'indent must be a non-negative integer, was $indent.');
+  }
+}
+
 class CliArgumentException implements Exception {
   CliArgumentException(this.message);
 
@@ -284,3 +306,6 @@ class CliArgumentException implements Exception {
 }
 
 class CliHelpException implements Exception {}
+
+// Ignoring as CLI arguments are dynamically typed
+// ignore_for_file: avoid_annotating_with_dynamic
diff --git a/lib/src/cli/formatter.dart b/lib/src/cli/formatter.dart
index fc75ec0..bba085e 100644
--- a/lib/src/cli/formatter.dart
+++ b/lib/src/cli/formatter.dart
@@ -2,7 +2,7 @@ import 'dart:io';
 
 import 'arguments.dart';
 
-typedef CliArgumentFormatter = Object Function(Object arg);
+typedef CliArgumentFormatter = dynamic Function(dynamic arg);
 
 const _kArgumentFormatters = <CliArgument, CliArgumentFormatter>{
   CliArgument.svgDir: _dir,
@@ -12,11 +12,11 @@ const _kArgumentFormatters = <CliArgument, CliArgumentFormatter>{
   CliArgument.configFile: _file,
 };
 
-Directory _dir(Object arg) => arg == null ? null : Directory(arg as String);
+Directory _dir(dynamic arg) => Directory(arg as String);
 
-File _file(Object arg) => arg == null ? null : File(arg as String);
+File _file(dynamic arg) => File(arg as String);
 
-int _indent(Object arg) {
+int _indent(dynamic arg) {
   if (arg is int) {
     return arg;
   }
@@ -29,13 +29,11 @@ int _indent(Object arg) {
     throwException();
   }
 
-  int indent;
+  late final int indent;
   final indentArg = arg as String;
 
   try {
-    if (indentArg != null) {
-      indent = int.parse(indentArg);
-    }
+    indent = int.parse(indentArg);
   } on FormatException catch (_) {
     throwException();
   }
@@ -44,14 +42,17 @@ int _indent(Object arg) {
 }
 
 /// Formats arguments.
-Map<CliArgument, Object> formatArguments(Map<CliArgument, Object> args) {
-  return args.map((k, v) {
+Map<CliArgument, dynamic> formatArguments(Map<CliArgument, dynamic> args) {
+  return args.map<CliArgument, dynamic>((k, dynamic v) {
     final formatter = _kArgumentFormatters[k];
 
-    if (formatter == null) {
-      return MapEntry(k, v);
+    if (formatter == null || v == null) {
+      return MapEntry<CliArgument, dynamic>(k, v);
     }
 
-    return MapEntry(k, formatter(v));
+    return MapEntry<CliArgument, dynamic>(k, formatter(v));
   });
 }
+
+// Ignoring as CLI arguments are dynamically typed
+// ignore_for_file: avoid_annotating_with_dynamic
diff --git a/lib/src/cli/options.dart b/lib/src/cli/options.dart
index b76f612..8ef3427 100644
--- a/lib/src/cli/options.dart
+++ b/lib/src/cli/options.dart
@@ -6,27 +6,27 @@ void defineOptions(ArgParser argParser) {
   argParser
     ..addSeparator('Flutter class options:')
     ..addOption(
-      kOptionNames[CliArgument.classFile],
+      kOptionNames[CliArgument.classFile]!,
       abbr: 'o',
       help:
           'Output path for Flutter-compatible class that contains identifiers for the icons.',
       valueHelp: 'path',
     )
     ..addOption(
-      kOptionNames[CliArgument.indent],
+      kOptionNames[CliArgument.indent]!,
       abbr: 'i',
       help: 'Number of spaces in leading indentation for Flutter class file.',
       valueHelp: 'indent',
       defaultsTo: '2',
     )
     ..addOption(
-      kOptionNames[CliArgument.className],
+      kOptionNames[CliArgument.className]!,
       abbr: 'c',
       help: 'Name for a generated class.',
       valueHelp: 'name',
     )
     ..addOption(
-      kOptionNames[CliArgument.fontPackage],
+      kOptionNames[CliArgument.fontPackage]!,
       abbr: 'p',
       help:
           'Name of a package that provides a font. Used to provide a font through package dependency.',
@@ -34,46 +34,46 @@ void defineOptions(ArgParser argParser) {
     )
     ..addSeparator('Font options:')
     ..addOption(
-      kOptionNames[CliArgument.fontName],
+      kOptionNames[CliArgument.fontName]!,
       abbr: 'f',
       help: 'Name for a generated font.',
       valueHelp: 'name',
     )
     ..addFlag(
-      kOptionNames[CliArgument.normalize],
+      kOptionNames[CliArgument.normalize]!,
       help:
           'Enables glyph normalization for the font. Disable this if every icon has the same size and positioning.',
       defaultsTo: true,
     )
     ..addFlag(
-      kOptionNames[CliArgument.ignoreShapes],
+      kOptionNames[CliArgument.ignoreShapes]!,
       help: 'Disables SVG shape-to-path conversion (circle, rect, etc.).',
       defaultsTo: true,
     )
     ..addSeparator('Other options:')
     ..addOption(
-      kOptionNames[CliArgument.configFile],
+      kOptionNames[CliArgument.configFile]!,
       abbr: 'z',
       help:
           'Path to Fontify yaml configuration file. pubspec.yaml and fontify.yaml files are used by default.',
       valueHelp: 'path',
     )
     ..addFlag(
-      kOptionNames[CliArgument.recursive],
+      kOptionNames[CliArgument.recursive]!,
       abbr: 'r',
       help: 'Recursively look for .svg files.',
       defaultsTo: kDefaultRecursive,
       negatable: false,
     )
     ..addFlag(
-      kOptionNames[CliArgument.verbose],
+      kOptionNames[CliArgument.verbose]!,
       abbr: 'v',
       help: 'Display every logging message.',
       defaultsTo: kDefaultVerbose,
       negatable: false,
     )
     ..addFlag(
-      kOptionNames[CliArgument.help],
+      kOptionNames[CliArgument.help]!,
       abbr: 'h',
       help: 'Shows this usage information.',
       negatable: false,
diff --git a/lib/src/common/api.dart b/lib/src/common/api.dart
index 7e6ff7e..4e976f9 100644
--- a/lib/src/common/api.dart
+++ b/lib/src/common/api.dart
@@ -1,5 +1,3 @@
-import 'package:meta/meta.dart';
-
 import '../otf.dart';
 import '../svg.dart';
 import '../utils/flutter_class_gen.dart';
@@ -30,12 +28,11 @@ class SvgToOtfResult {
 ///
 /// Returns an instance of [SvgToOtfResult] class containing glyphs and a font.
 SvgToOtfResult svgToOtf({
-  @required Map<String, String> svgMap,
-  bool ignoreShapes,
-  bool normalize,
-  String fontName,
+  required Map<String, String> svgMap,
+  bool? ignoreShapes,
+  bool? normalize,
+  String? fontName,
 }) {
-  svgMap ??= {};
   normalize ??= true;
 
   final svgList = [
@@ -80,12 +77,12 @@ SvgToOtfResult svgToOtf({
 ///
 /// Returns content of a class file.
 String generateFlutterClass({
-  @required List<GenericGlyph> glyphList,
-  String className,
-  String familyName,
-  String fontFileName,
-  String package,
-  int indent,
+  required List<GenericGlyph> glyphList,
+  String? className,
+  String? familyName,
+  String? fontFileName,
+  String? package,
+  int? indent,
 }) {
   final generator = FlutterClassGenerator(
     glyphList,
diff --git a/lib/src/common/generic_glyph.dart b/lib/src/common/generic_glyph.dart
index e0ec97c..eb12e7c 100644
--- a/lib/src/common/generic_glyph.dart
+++ b/lib/src/common/generic_glyph.dart
@@ -17,8 +17,8 @@ import 'outline.dart';
 class GenericGlyphMetadata {
   GenericGlyphMetadata({this.charCode, this.name});
 
-  int charCode;
-  String name;
+  int? charCode;
+  String? name;
 
   /// Deep copy
   GenericGlyphMetadata copy() {
@@ -49,7 +49,7 @@ class GenericGlyphMetrics {
 /// Used as an intermediate storage between different types of glyphs
 /// (including OpenType's CharString, TrueType outlines).
 class GenericGlyph {
-  GenericGlyph(this.outlines, this.bounds, [GenericGlyphMetadata metadata])
+  GenericGlyph(this.outlines, this.bounds, [GenericGlyphMetadata? metadata])
       : metadata = metadata ?? GenericGlyphMetadata();
 
   GenericGlyph.empty()
@@ -212,21 +212,20 @@ class GenericGlyph {
   }
 
   /// Resizes according to ascender/descender or a font height.
-  GenericGlyph resize({int ascender, int descender, int fontHeight}) {
-    assert((ascender != null && descender != null) || fontHeight != null,
-        'Wrong parameters for resizing');
-
+  GenericGlyph resize({int? ascender, int? descender, int? fontHeight}) {
     final metrics = this.metrics;
 
-    int longestSide;
-    double sideRatio;
+    late final int longestSide;
+    late final double sideRatio;
 
-    if (fontHeight == null) {
+    if (ascender != null && descender != null) {
       longestSide = math.max(metrics.height, metrics.width);
       sideRatio = (ascender + descender) / longestSide;
-    } else {
+    } else if (fontHeight != null) {
       longestSide = bounds.height.toInt();
       sideRatio = fontHeight / longestSide;
+    } else {
+      throw ArgumentError('Wrong parameters for resizing');
     }
 
     // No need to resize
diff --git a/lib/src/otf/cff/char_string.dart b/lib/src/otf/cff/char_string.dart
index f9f4683..5e55ceb 100644
--- a/lib/src/otf/cff/char_string.dart
+++ b/lib/src/otf/cff/char_string.dart
@@ -11,7 +11,7 @@ import 'operand.dart';
 import 'operator.dart';
 
 class CharStringOperand extends CFFOperand {
-  CharStringOperand(num value, [int size]) : super(value, size);
+  CharStringOperand(num? value, [int? size]) : super(value, size);
 
   factory CharStringOperand.fromByteData(
       ByteData byteData, int offset, int b0) {
@@ -31,7 +31,7 @@ class CharStringOperand extends CFFOperand {
     if (value is double) {
       byteData
         ..setUint8(offset++, 255)
-        ..setUint32(offset, (value * 0x10000).round().toInt());
+        ..setUint32(offset, (value! * 0x10000).round().toInt());
       offset += 4;
     } else {
       super.encodeToBinary(byteData);
@@ -211,7 +211,7 @@ class CharStringInterpreter {
     }
   }
 
-  void _pushCommand(Iterable<num> operandValues, int opB0, [int opB1]) {
+  void _pushCommand(Iterable<num?> operandValues, int opB0, [int? opB1]) {
     final command = CharStringCommand(
         CFFOperator(CFFOperatorContext.charString, opB0, opB1),
         operandValues.map((e) => CharStringOperand(e)).toList());
@@ -232,7 +232,7 @@ class CharStringInterpreter {
       if (op == 28 || op >= 32) {
         final operandByteData = byteData.sublistView(offset);
         final operand = CharStringOperand.fromByteData(operandByteData, 0, op);
-        _stack.add(operand.value);
+        _stack.add(operand.value!);
       } else {
         switch (op) {
           case 1: // hstem
@@ -249,7 +249,7 @@ class CharStringInterpreter {
             break;
 
           case 5: // rlineto
-            final arguments = <num>[];
+            final arguments = <num?>[];
 
             while (_stack.length >= 2) {
               final dx = _stack.removeFirstOrZero();
@@ -263,7 +263,7 @@ class CharStringInterpreter {
 
           case 6: // hlineto
           case 7: // vlineto
-            final arguments = <num>[];
+            final arguments = <num?>[];
             var isX = op == 6;
 
             while (_stack.isNotEmpty) {
@@ -282,7 +282,7 @@ class CharStringInterpreter {
             break;
 
           case 8: // rrcurveto
-            final arguments = <num>[];
+            final arguments = <num?>[];
 
             while (_stack.length >= 6) {
               final dxc1 = _stack.removeFirstOrZero();
@@ -332,7 +332,7 @@ class CharStringInterpreter {
             break;
 
           case 24: // rcurveline
-            final arguments = <num>[];
+            final arguments = <num?>[];
 
             while (_stack.length >= 8) {
               final dxc1 = _stack.removeFirstOrZero();
@@ -352,7 +352,7 @@ class CharStringInterpreter {
             break;
 
           case 25: // rlinecurve
-            final arguments = <num>[];
+            final arguments = <num?>[];
 
             while (_stack.length >= 8) {
               final dx = _stack.removeFirstOrZero();
@@ -372,7 +372,7 @@ class CharStringInterpreter {
             break;
 
           case 26: // vvcurveto
-            final arguments = <num>[];
+            final arguments = <num?>[];
 
             if (_stack.length.isOdd) {
               final dx = _stack.removeFirstOrZero();
@@ -393,7 +393,7 @@ class CharStringInterpreter {
             break;
 
           case 27: // hhcurveto
-            final arguments = <num>[];
+            final arguments = <num?>[];
 
             if (_stack.length.isOdd) {
               final dy = _stack.removeFirstOrZero();
@@ -416,7 +416,7 @@ class CharStringInterpreter {
           case 30: // vhcurveto
           case 31: // hvcurveto
             var isX = op == 31;
-            final arguments = <num>[];
+            final arguments = <num?>[];
 
             while (_stack.length >= 4) {
               if (isX) {
@@ -482,7 +482,7 @@ class CharStringInterpreter {
 
   ByteData writeCommands(
     List<CharStringCommand> commandList, {
-    int glyphWidth,
+    int? glyphWidth,
   }) {
     final list = <int>[];
 
@@ -519,7 +519,7 @@ class CharStringInterpreterLimits {
 }
 
 extension _QueueExt<T> on Queue<T> {
-  T removeFirstOrZero() {
+  T? removeFirstOrZero() {
     if (isEmpty) {
       if (T == num) {
         return 0 as T;
diff --git a/lib/src/otf/cff/charset.dart b/lib/src/otf/cff/charset.dart
index da2b1a7..219f487 100644
--- a/lib/src/otf/cff/charset.dart
+++ b/lib/src/otf/cff/charset.dart
@@ -9,9 +9,9 @@ const _kRange1Size = 3;
 abstract class CharsetEntry implements BinaryCodable {
   const CharsetEntry(this.format);
 
-  factory CharsetEntry.fromByteData(ByteData byteData, int glyphCount) {
-    final format = byteData.getUint8(0);
-    byteData = byteData.sublistView(1);
+  static CharsetEntry? fromByteData(ByteData bd, int glyphCount) {
+    final format = bd.getUint8(0);
+    final byteData = bd.sublistView(1);
 
     switch (format) {
       case _kFormat1:
diff --git a/lib/src/otf/cff/dict.dart b/lib/src/otf/cff/dict.dart
index 03f1060..b9ce40e 100644
--- a/lib/src/otf/cff/dict.dart
+++ b/lib/src/otf/cff/dict.dart
@@ -1,4 +1,5 @@
 import 'dart:typed_data';
+import 'package:collection/collection.dart';
 
 import '../../common/codable/binary.dart';
 import '../../utils/exception.dart';
@@ -21,7 +22,7 @@ class CFFDictEntry extends BinaryCodable {
 
       if (b0 < 28) {
         /// Reading an operator (b0 is not in operand range)
-        int b1;
+        int? b1;
 
         if (b0 == _kOperatorEscapeByte) {
           /// An operator is 2-byte long
@@ -112,9 +113,8 @@ class CFFDict extends BinaryCodable {
 
   List<CFFDictEntry> entryList;
 
-  CFFDictEntry getEntryForOperator(CFFOperator operator) {
-    return entryList.firstWhere((e) => e.operator == operator,
-        orElse: () => null);
+  CFFDictEntry? getEntryForOperator(CFFOperator operator) {
+    return entryList.firstWhereOrNull((e) => e.operator == operator);
   }
 
   @override
diff --git a/lib/src/otf/cff/index.dart b/lib/src/otf/cff/index.dart
index 59faeb0..eef91c6 100644
--- a/lib/src/otf/cff/index.dart
+++ b/lib/src/otf/cff/index.dart
@@ -11,7 +11,7 @@ class CFFIndex extends BinaryCodable {
 
   CFFIndex.empty(this.isCFF1)
       : count = 0,
-        offSize = null,
+        offSize = 1,
         offsetList = [];
 
   factory CFFIndex.fromByteData(ByteData byteData, bool isCFF1) {
@@ -25,10 +25,7 @@ class CFFIndex extends BinaryCodable {
     }
 
     final offSize = byteData.getUint8(offset++);
-
-    if (offSize < 1 || offSize > 4) {
-      throw TableDataFormatException('Wrong offSize value');
-    }
+    _validateOffSize(offSize);
 
     final offsetList = <int>[];
 
@@ -53,8 +50,16 @@ class CFFIndex extends BinaryCodable {
 
   bool get isEmpty => count == 0;
 
+  static void _validateOffSize(int offSize) {
+    if (offSize < 1 || offSize > 4) {
+      throw TableDataFormatException('Wrong offSize value');
+    }
+  }
+
   @override
   void encodeToBinary(ByteData byteData) {
+    _validateOffSize(offSize);
+
     var offset = 0;
 
     if (isCFF1) {
@@ -126,7 +131,7 @@ class CFFIndexWithData<T> implements BinaryCodable, CalculatableOffsets {
   factory CFFIndexWithData.create(List<T> data, bool isCFF1) =>
       CFFIndexWithData(null, data, isCFF1);
 
-  CFFIndex index;
+  CFFIndex? index;
   final List<T> data;
   final bool isCFF1;
 
@@ -218,8 +223,18 @@ class CFFIndexWithData<T> implements BinaryCodable, CalculatableOffsets {
     return newIndex.size + newIndex.offsetList.last - 1;
   }
 
+  CFFIndex get _guardedIndex {
+    if (index == null) {
+      throw StateError('index must not be null');
+    }
+
+    return index!;
+  }
+
   @override
   void encodeToBinary(ByteData byteData) {
+    final index = _guardedIndex;
+
     if (data.isEmpty) {
       index.encodeToBinary(byteData.sublistView(0, index.size));
     }
diff --git a/lib/src/otf/cff/operand.dart b/lib/src/otf/cff/operand.dart
index c659be2..6fc405c 100644
--- a/lib/src/otf/cff/operand.dart
+++ b/lib/src/otf/cff/operand.dart
@@ -113,17 +113,17 @@ class CFFOperand extends BinaryCodable {
   }
 
   /// Either real or integer number
-  final num value;
+  final num? value;
 
   /// Weather should force max-length integer or not (used for offset pointers)
   final bool forceLargeInt;
 
-  int _size;
+  int? _size;
 
   /// Returns normalized string representation of a real number
   String _doubleToNormalizedString() {
     if (value is! double) {
-      return null;
+      throw StateError('Value type is not double');
     }
 
     var string = value.toString();
@@ -140,15 +140,24 @@ class CFFOperand extends BinaryCodable {
     return string;
   }
 
+  num get _guardedValue {
+    if (value == null) {
+      throw StateError('Value must not be null');
+    }
+
+    return value!;
+  }
+
   @override
   void encodeToBinary(ByteData byteData) {
     var offset = 0;
+    final value = _guardedValue;
 
     void writeDouble() {
       final s = _doubleToNormalizedString();
 
       var firstHalf = true;
-      int prevNibble;
+      late int prevNibble;
 
       for (var i = 0; i < s.length; i++) {
         var char = s[i];
@@ -213,9 +222,11 @@ class CFFOperand extends BinaryCodable {
   @override
   int get size {
     if (_size != null) {
-      return _size;
+      return _size!;
     }
 
+    final value = _guardedValue;
+
     return _size = () {
       if (value is double) {
         var valueString = _doubleToNormalizedString();
diff --git a/lib/src/otf/cff/operator.dart b/lib/src/otf/cff/operator.dart
index a65471a..194e6bc 100644
--- a/lib/src/otf/cff/operator.dart
+++ b/lib/src/otf/cff/operator.dart
@@ -14,7 +14,7 @@ class CFFOperator implements BinaryCodable {
       : intValue = b1 != null ? ((b0 << 8) | b1) : b0;
 
   final int b0;
-  final int b1;
+  final int? b1;
   final int intValue;
   final CFFOperatorContext context;
 
@@ -38,7 +38,7 @@ class CFFOperator implements BinaryCodable {
     byteData.setUint8(0, b0);
 
     if (b1 != null) {
-      byteData.setUint8(1, b1);
+      byteData.setUint8(1, b1!);
     }
   }
 
@@ -48,10 +48,14 @@ class CFFOperator implements BinaryCodable {
 
     switch (context) {
       case CFFOperatorContext.dict:
-        name = dictOperatorNames[this];
+        if (dictOperatorNames.containsKey(this)) {
+          name = dictOperatorNames[this]!;
+        }
         break;
       case CFFOperatorContext.charString:
-        name = charStringOperatorNames[this];
+        if (charStringOperatorNames.containsKey(this)) {
+          name = charStringOperatorNames[this]!;
+        }
         break;
     }
 
diff --git a/lib/src/otf/otf.dart b/lib/src/otf/otf.dart
index 47e13d6..fd45270 100644
--- a/lib/src/otf/otf.dart
+++ b/lib/src/otf/otf.dart
@@ -1,10 +1,9 @@
 import 'dart:typed_data';
 
-import 'package:meta/meta.dart';
-
 import '../common/calculatable_offsets.dart';
 import '../common/codable/binary.dart';
 import '../common/generic_glyph.dart';
+import '../utils.dart';
 import '../utils/misc.dart';
 import '../utils/otf.dart';
 
@@ -64,14 +63,14 @@ class OpenTypeFont implements BinaryCodable {
   /// glyphs are resized and centered to fit in coordinates grid (unitsPerEm).
   /// Defaults to true.
   factory OpenTypeFont.createFromGlyphs({
-    @required List<GenericGlyph> glyphList,
-    String fontName,
-    String description,
-    Revision revision,
-    String achVendID,
-    bool useOpenType,
-    bool usePostV2,
-    bool normalize,
+    required List<GenericGlyph> glyphList,
+    String? fontName,
+    String? description,
+    Revision? revision,
+    String? achVendID,
+    bool? useOpenType,
+    bool? usePostV2,
+    bool? normalize,
   }) {
     if (fontName?.isEmpty ?? false) {
       fontName = null;
@@ -126,12 +125,17 @@ class OpenTypeFont implements BinaryCodable {
         HeaderTable.create(glyphMetricsList, glyf, revision, unitsPerEm);
     final loca = useOpenType
         ? null
-        : IndexToLocationTable.create(head.indexToLocFormat, glyf);
+        : IndexToLocationTable.create(head.indexToLocFormat, glyf!);
     final hmtx = HorizontalMetricsTable.create(glyphMetricsList, unitsPerEm);
     final hhea = HorizontalHeaderTable.create(
         glyphMetricsList, hmtx, ascender, descender);
     final post = PostScriptTable.create(resizedGlyphList, usePostV2);
     final name = NamingTable.create(fontName, description, revision);
+
+    if (name == null) {
+      throw TableDataFormatException('Unknown "name" table format');
+    }
+
     final maxp = MaximumProfileTable.create(fullGlyphList.length, glyf);
     final cmap = CharacterToGlyphTable.create(fullGlyphList);
     final gsub = GlyphSubstitutionTable.create();
@@ -140,13 +144,13 @@ class OpenTypeFont implements BinaryCodable {
     final cff =
         useOpenType ? CFF1Table.create(fullGlyphList, head, hmtx, name) : null;
 
-    final tables = {
+    final tables = <String, FontTable>{
       if (!useOpenType) ...{
-        kGlyfTag: glyf,
-        kLocaTag: loca,
+        kGlyfTag: glyf!,
+        kLocaTag: loca!,
       },
       if (useOpenType) ...{
-        kCFFTag: cff,
+        kCFFTag: cff!,
       },
       kCmapTag: cmap,
       kMaxpTag: maxp,
@@ -212,7 +216,7 @@ class OpenTypeFont implements BinaryCodable {
 
       table.entry = TableRecordEntry(tag, calculateTableChecksum(encodedTable),
           currentTableOffset, tableSize);
-      entryList.add(table.entry);
+      entryList.add(table.entry!);
 
       currentTableOffset += getPaddedTableSize(tableSize);
     }
@@ -231,7 +235,7 @@ class OpenTypeFont implements BinaryCodable {
 
     // Setting checksum for whole font in the head table
     final fontChecksum = calculateFontChecksum(byteData);
-    byteData.setUint32(head.entry.offset + 8, fontChecksum);
+    byteData.setUint32(head.entry!.offset + 8, fontChecksum);
   }
 
   int get entryListSize => kTableRecordEntryLength * tableMap.length;
@@ -245,9 +249,9 @@ class OpenTypeFont implements BinaryCodable {
   // TODO: I don't like this. Refactor it later. Use "strategy" or something.
   static List<GenericGlyph> _resizeAndCenter(
     List<GenericGlyph> glyphList, {
-    int ascender,
-    int descender,
-    int fontHeight,
+    int? ascender,
+    int? descender,
+    int? fontHeight,
   }) {
     return glyphList.map((g) {
       if (fontHeight != null) {
@@ -255,9 +259,13 @@ class OpenTypeFont implements BinaryCodable {
         return g.resize(fontHeight: fontHeight);
       }
 
-      return g
-          .resize(ascender: ascender, descender: descender)
-          .center(ascender, descender);
+      if (ascender != null && descender != null) {
+        return g
+            .resize(ascender: ascender, descender: descender)
+            .center(ascender, descender);
+      }
+
+      throw ArgumentError('ascender/descender or fontHeight must not be null');
     }).toList();
   }
 
diff --git a/lib/src/otf/reader.dart b/lib/src/otf/reader.dart
index 9b54c1f..038fd42 100644
--- a/lib/src/otf/reader.dart
+++ b/lib/src/otf/reader.dart
@@ -13,8 +13,8 @@ class OTFReader {
 
   final ByteData _byteData;
 
-  OffsetTable _offsetTable;
-  OpenTypeFont _font;
+  late OffsetTable _offsetTable;
+  late OpenTypeFont _font;
 
   /// Tables by tags
   final _tableMap = <String, FontTable>{};
@@ -66,7 +66,7 @@ class OTFReader {
         continue;
       }
 
-      final table = _createTableFromEntry(entryMap[tag]);
+      final table = _createTableFromEntry(entry);
 
       if (table == null) {
         continue;
@@ -76,7 +76,7 @@ class OTFReader {
     }
   }
 
-  FontTable _createTableFromEntry(TableRecordEntry entry) {
+  FontTable? _createTableFromEntry(TableRecordEntry entry) {
     switch (entry.tag) {
       case kHeadTag:
         return HeaderTable.fromByteData(_byteData, entry);
@@ -118,20 +118,22 @@ class OTFReader {
   void _validateChecksums() {
     final byteDataCopy = ByteData.sublistView(
         Uint8List.fromList([..._byteData.buffer.asUint8List().toList()]))
-      ..setUint32(_font.head.entry.offset + 8,
+      ..setUint32(_font.head.entry!.offset + 8,
           0); // Setting head table's checkSumAdjustment to 0
 
     for (final table in _font.tableMap.values) {
-      final tableOffset = table.entry.offset;
-      final tableLength = table.entry.length;
+      final entry = table.entry!;
+
+      final tableOffset = entry.offset;
+      final tableLength = entry.length;
 
       final tableByteData = ByteData.sublistView(
           byteDataCopy, tableOffset, tableOffset + tableLength);
       final actualChecksum = calculateTableChecksum(tableByteData);
-      final expectedChecksum = table.entry.checkSum;
+      final expectedChecksum = entry.checkSum;
 
       if (actualChecksum != expectedChecksum) {
-        throw ChecksumException.table(table.entry.tag);
+        throw ChecksumException.table(entry.tag);
       }
     }
 
diff --git a/lib/src/otf/table/abstract.dart b/lib/src/otf/table/abstract.dart
index e52dd6b..14add69 100644
--- a/lib/src/otf/table/abstract.dart
+++ b/lib/src/otf/table/abstract.dart
@@ -4,5 +4,5 @@ import 'table_record_entry.dart';
 abstract class FontTable implements BinaryCodable {
   FontTable.fromTableRecordEntry(this.entry);
 
-  TableRecordEntry entry;
+  TableRecordEntry? entry;
 }
diff --git a/lib/src/otf/table/cff.dart b/lib/src/otf/table/cff.dart
index 2d7381f..ea946f0 100644
--- a/lib/src/otf/table/cff.dart
+++ b/lib/src/otf/table/cff.dart
@@ -31,10 +31,10 @@ const _kMajorVersion1 = 0x0001;
 const _kMajorVersion2 = 0x0002;
 
 abstract class CFFTable extends FontTable {
-  CFFTable.fromTableRecordEntry(TableRecordEntry entry)
+  CFFTable.fromTableRecordEntry(TableRecordEntry? entry)
       : super.fromTableRecordEntry(entry);
 
-  factory CFFTable.fromByteData(ByteData byteData, TableRecordEntry entry) {
+  static CFFTable? fromByteData(ByteData byteData, TableRecordEntry entry) {
     final major = byteData.getUint8(entry.offset);
 
     switch (major) {
@@ -54,11 +54,12 @@ abstract class CFFTable extends FontTable {
 void _calculateEntryOffsets(
   List<CFFDictEntry> entryList,
   List<int> offsetList, {
-  int operandIndex,
-  List<int> operandIndexList,
+  int? operandIndex,
+  List<int>? operandIndexList,
 }) {
-  assert(operandIndex != null || operandIndexList != null,
-      'Specify operand index');
+  if (operandIndex == null && operandIndexList == null) {
+    throw ArgumentError.notNull('Specify operand index');
+  }
 
   bool sizeChanged;
 
@@ -68,7 +69,7 @@ void _calculateEntryOffsets(
     sizeChanged = false;
 
     for (var i = 0; i < entryList.length; i++) {
-      final entryOperandIndex = operandIndex ?? operandIndexList[i];
+      final entryOperandIndex = operandIndex ?? operandIndexList![i];
       final entry = entryList[i];
       final oldOperand = entry.operandList[entryOperandIndex];
       final newOperand = CFFOperand.fromValue(offsetList[i]);
diff --git a/lib/src/otf/table/cff1.dart b/lib/src/otf/table/cff1.dart
index 187cc9f..0ef9a29 100644
--- a/lib/src/otf/table/cff1.dart
+++ b/lib/src/otf/table/cff1.dart
@@ -27,7 +27,7 @@ class CFF1TableHeader implements BinaryCodable {
   final int majorVersion;
   final int minorVersion;
   final int headerSize;
-  int offSize;
+  int? offSize;
 
   @override
   void encodeToBinary(ByteData byteData) {
@@ -35,7 +35,7 @@ class CFF1TableHeader implements BinaryCodable {
       ..setUint8(0, majorVersion)
       ..setUint8(1, minorVersion)
       ..setUint8(2, headerSize)
-      ..setUint8(3, offSize);
+      ..setUint8(3, offSize!);
   }
 
   @override
@@ -44,7 +44,7 @@ class CFF1TableHeader implements BinaryCodable {
 
 class CFF1Table extends CFFTable implements CalculatableOffsets {
   CFF1Table(
-    TableRecordEntry entry,
+    TableRecordEntry? entry,
     this.header,
     this.nameIndex,
     this.topDicts,
@@ -94,10 +94,10 @@ class CFF1Table extends CFFTable implements CalculatableOffsets {
       byteData.sublistView(fixedOffset),
       true,
     );
-    fixedOffset += globalSubrsData.index.size;
+    fixedOffset += globalSubrsData.index!.size;
 
     /// CharStrings INDEX
-    final charStringsIndexEntry = topDict.getEntryForOperator(op.charStrings);
+    final charStringsIndexEntry = topDict.getEntryForOperator(op.charStrings)!;
     final charStringsIndexOffset =
         charStringsIndexEntry.operandList.first.value as int;
     final charStringsIndexByteData =
@@ -110,16 +110,16 @@ class CFF1Table extends CFFTable implements CalculatableOffsets {
 
     /// Charsets
     final charsetsOffset =
-        topDict.getEntryForOperator(op.charset).operandList.first.value as int;
+        topDict.getEntryForOperator(op.charset)!.operandList.first.value as int;
     final charsetsByteData =
         byteData.sublistView(entry.offset + charsetsOffset);
 
     final charsetEntry = CharsetEntry.fromByteData(
       charsetsByteData,
-      charStringsData.index.count,
-    );
+      charStringsData.index!.count,
+    )!;
 
-    final privateEntry = topDict.getEntryForOperator(op.private);
+    final privateEntry = topDict.getEntryForOperator(op.private)!;
     final dictOffset =
         entry.offset + (privateEntry.operandList.last.value as int);
     final dictLength = privateEntry.operandList.first.value as int;
@@ -186,13 +186,13 @@ class CFF1Table extends CFFTable implements CalculatableOffsets {
       if (standardSid != null) {
         sidList.add(standardSid);
       } else {
-        putStringInIndex(g.metadata.name);
+        putStringInIndex(g.metadata.name!);
       }
     }
 
     final glyphSidList = [...sidList];
 
-    final fontName = name.getStringByNameId(NameID.fullFontName);
+    final fontName = name.getStringByNameId(NameID.fullFontName)!;
     final copyrightString = '${name.getStringByNameId(NameID.copyright)} '
         '${name.getStringByNameId(NameID.urlVendor)}';
 
@@ -206,10 +206,11 @@ class CFF1Table extends CFFTable implements CalculatableOffsets {
     final topDicts = CFFIndexWithData.create([
       CFFDict([
         for (final e in topDictStringEntryMap.entries)
-          CFFDictEntry(
-            [CFFOperand.fromValue(putStringInIndex(e.value))],
-            e.key,
-          ),
+          if (e.value != null)
+            CFFDictEntry(
+              [CFFOperand.fromValue(putStringInIndex(e.value!))],
+              e.key,
+            ),
         CFFDictEntry([
           CFFOperand.fromValue(head.xMin),
           CFFOperand.fromValue(head.yMin),
@@ -330,9 +331,9 @@ class CFF1Table extends CFFTable implements CalculatableOffsets {
     final privateDictOffset = offset;
     offset += privateDict.size;
 
-    final charsetEntry = topDict.getEntryForOperator(op.charset);
-    final charStringsEntry = topDict.getEntryForOperator(op.charStrings);
-    final privateEntry = topDict.getEntryForOperator(op.private);
+    final charsetEntry = topDict.getEntryForOperator(op.charset)!;
+    final charStringsEntry = topDict.getEntryForOperator(op.charStrings)!;
+    final privateEntry = topDict.getEntryForOperator(op.private)!;
 
     final offsetList = [
       charsetOffset,
@@ -363,7 +364,7 @@ class CFF1Table extends CFFTable implements CalculatableOffsets {
     localSubrsDataList.forEach((e) => e.recalculateOffsets());
 
     // Last data offset
-    final lastDataEntry = topDict.getEntryForOperator(op.private);
+    final lastDataEntry = topDict.getEntryForOperator(op.private)!;
     final lastDataOffset = lastDataEntry.operandList.last.value as int;
     header.offSize = (lastDataOffset.bitLength / 8).ceil();
   }
diff --git a/lib/src/otf/table/cff2.dart b/lib/src/otf/table/cff2.dart
index 98f05f9..5cbd0cf 100644
--- a/lib/src/otf/table/cff2.dart
+++ b/lib/src/otf/table/cff2.dart
@@ -21,7 +21,7 @@ class CFF2TableHeader implements BinaryCodable {
   final int majorVersion;
   final int minorVersion;
   final int headerSize;
-  int topDictLength;
+  int? topDictLength;
 
   @override
   void encodeToBinary(ByteData byteData) {
@@ -29,7 +29,7 @@ class CFF2TableHeader implements BinaryCodable {
       ..setUint8(0, majorVersion)
       ..setUint8(1, minorVersion)
       ..setUint8(2, headerSize)
-      ..setUint16(3, topDictLength);
+      ..setUint16(3, topDictLength!);
   }
 
   @override
@@ -38,7 +38,7 @@ class CFF2TableHeader implements BinaryCodable {
 
 class CFF2Table extends CFFTable implements CalculatableOffsets {
   CFF2Table(
-    TableRecordEntry entry,
+    TableRecordEntry? entry,
     this.header,
     this.topDict,
     this.globalSubrsData,
@@ -61,15 +61,15 @@ class CFF2Table extends CFFTable implements CalculatableOffsets {
     fixedOffset += _kCFF2HeaderSize;
 
     final topDict = CFFDict.fromByteData(
-        byteData.sublistView(fixedOffset, header.topDictLength));
-    fixedOffset += header.topDictLength;
+        byteData.sublistView(fixedOffset, header.topDictLength!));
+    fixedOffset += header.topDictLength!;
 
     final globalSubrsData = CFFIndexWithData<Uint8List>.fromByteData(
         byteData.sublistView(fixedOffset), false);
-    fixedOffset += globalSubrsData.index.size;
+    fixedOffset += globalSubrsData.index!.size;
 
     /// CharStrings INDEX
-    final charStringsIndexEntry = topDict.getEntryForOperator(op.charStrings);
+    final charStringsIndexEntry = topDict.getEntryForOperator(op.charStrings)!;
     final charStringsIndexOffset =
         charStringsIndexEntry.operandList.first.value as int;
     final charStringsIndexByteData =
@@ -80,7 +80,7 @@ class CFF2Table extends CFFTable implements CalculatableOffsets {
 
     /// VariationStore
     final vstoreEntry = topDict.getEntryForOperator(op.vstore);
-    VariationStoreData vstoreData;
+    VariationStoreData? vstoreData;
 
     if (vstoreEntry != null) {
       final vstoreOffset = vstoreEntry.operandList.first.value as int;
@@ -91,7 +91,7 @@ class CFF2Table extends CFFTable implements CalculatableOffsets {
     // NOTE: not decoding FDSelect - using single Font DICT only
 
     /// Font DICT INDEX
-    final fdArrayEntry = topDict.getEntryForOperator(op.fdArray);
+    final fdArrayEntry = topDict.getEntryForOperator(op.fdArray)!;
     final fdArrayOffset = fdArrayEntry.operandList.first.value as int;
 
     final fontIndexByteData =
@@ -107,8 +107,9 @@ class CFF2Table extends CFFTable implements CalculatableOffsets {
     /// Local subroutines for each Private DICT
     final localSubrsDataList = <CFFIndexWithData<Uint8List>>[];
 
-    for (var i = 0; i < fontDictList.index.count; i++) {
-      final privateEntry = fontDictList.data[i].getEntryForOperator(op.private);
+    for (var i = 0; i < fontDictList.index!.count; i++) {
+      final privateEntry =
+          fontDictList.data[i].getEntryForOperator(op.private)!;
       final dictOffset =
           entry.offset + (privateEntry.operandList.last.value as int);
       final dictLength = privateEntry.operandList.first.value as int;
@@ -140,7 +141,7 @@ class CFF2Table extends CFFTable implements CalculatableOffsets {
     final header = CFF2TableHeader.create();
     final topDict = CFFDict.empty();
     final globalSubrsData = CFFIndexWithData<Uint8List>.create([], false);
-    const VariationStoreData vstoreData = null; // omitted - no variations
+    const VariationStoreData? vstoreData = null; // omitted - no variations
 
     final charStringInterpreter = CharStringInterpreter(false);
 
@@ -190,7 +191,7 @@ class CFF2Table extends CFFTable implements CalculatableOffsets {
   final CFFDict topDict;
   final CFFIndexWithData<Uint8List> globalSubrsData;
   final CFFIndexWithData<Uint8List> charStringsData;
-  final VariationStoreData vstoreData;
+  final VariationStoreData? vstoreData;
   final CFFIndexWithData<CFFDict> fontDictList;
   final List<CFFDict> privateDictList;
   final List<CFFIndexWithData<Uint8List>> localSubrsDataList;
@@ -213,10 +214,10 @@ class CFF2Table extends CFFTable implements CalculatableOffsets {
 
     var offset = header.size + globalSubrsData.size + topDict.size;
 
-    int vstoreOffset;
+    int? vstoreOffset;
     if (vstoreData != null) {
       vstoreOffset = offset;
-      offset += vstoreData.size;
+      offset += vstoreData!.size;
     }
 
     final charStringsOffset = offset;
@@ -226,11 +227,11 @@ class CFF2Table extends CFFTable implements CalculatableOffsets {
     offset += fontDictList.size;
 
     final vstoreEntry = topDict.getEntryForOperator(op.vstore);
-    final charStringsEntry = topDict.getEntryForOperator(op.charStrings);
-    final fdArrayEntry = topDict.getEntryForOperator(op.fdArray);
+    final charStringsEntry = topDict.getEntryForOperator(op.charStrings)!;
+    final fdArrayEntry = topDict.getEntryForOperator(op.fdArray)!;
 
     final offsetList = [
-      if (vstoreData != null) vstoreOffset,
+      if (vstoreData != null) vstoreOffset!,
       charStringsOffset,
       fdArrayOffset,
     ];
@@ -255,15 +256,15 @@ class CFF2Table extends CFFTable implements CalculatableOffsets {
     charStringsData.recalculateOffsets();
 
     // Recalculating font DICTs private offsets and SUBRS entries offsets
-    final fdArrayEntry = topDict.getEntryForOperator(op.fdArray);
+    final fdArrayEntry = topDict.getEntryForOperator(op.fdArray)!;
     final fdArrayOffset = fdArrayEntry.operandList.first.value as int;
 
-    var fontDictOffset = fdArrayOffset + fontDictList.index.size;
+    var fontDictOffset = fdArrayOffset + fontDictList.index!.size;
 
     for (var i = 0; i < fontDictList.data.length; i++) {
       final fontDict = fontDictList.data[i];
       final privateDict = privateDictList[i];
-      final privateEntry = fontDict.getEntryForOperator(op.private);
+      final privateEntry = fontDict.getEntryForOperator(op.private)!;
 
       final newOperands = [
         CFFOperand.fromValue(privateDict.size),
@@ -308,8 +309,8 @@ class CFF2Table extends CFFTable implements CalculatableOffsets {
     offset += globalSubrsSize;
 
     if (vstoreData != null) {
-      final vstoreSize = vstoreData.size;
-      vstoreData.encodeToBinary(byteData.sublistView(offset, vstoreSize));
+      final vstoreSize = vstoreData!.size;
+      vstoreData!.encodeToBinary(byteData.sublistView(offset, vstoreSize));
       offset += vstoreSize;
     }
 
diff --git a/lib/src/otf/table/cmap.dart b/lib/src/otf/table/cmap.dart
index 340bc8d..f0c2171 100644
--- a/lib/src/otf/table/cmap.dart
+++ b/lib/src/otf/table/cmap.dart
@@ -71,7 +71,7 @@ class EncodingRecord implements BinaryCodable {
 
   final int platformID;
   final int encodingID;
-  int offset;
+  int? offset;
 
   @override
   int get size => _kEncodingRecordSize;
@@ -81,7 +81,7 @@ class EncodingRecord implements BinaryCodable {
     byteData
       ..setUint16(0, platformID)
       ..setUint16(2, encodingID)
-      ..setUint32(4, offset);
+      ..setUint32(4, offset!);
   }
 }
 
@@ -153,7 +153,7 @@ class CharacterToGlyphTableHeader implements BinaryCodable {
 abstract class CmapData implements BinaryCodable {
   CmapData(this.format);
 
-  factory CmapData.fromByteData(ByteData byteData, int offset) {
+  static CmapData? fromByteData(ByteData byteData, int offset) {
     final format = byteData.getUint16(offset);
 
     switch (format) {
@@ -170,7 +170,7 @@ abstract class CmapData implements BinaryCodable {
     }
   }
 
-  factory CmapData.create(List<_Segment> segmentList, int format) {
+  static CmapData? create(List<_Segment> segmentList, int format) {
     switch (format) {
       case _kFormat0:
         return CmapByteEncodingTable.create();
@@ -462,7 +462,7 @@ class CmapSegmentedCoverageTable extends CmapData {
 
 class CharacterToGlyphTable extends FontTable {
   CharacterToGlyphTable(
-    TableRecordEntry entry,
+    TableRecordEntry? entry,
     this.header,
     this.data,
   ) : super.fromTableRecordEntry(entry);
@@ -473,16 +473,21 @@ class CharacterToGlyphTable extends FontTable {
   ) {
     final header = CharacterToGlyphTableHeader.fromByteData(byteData, entry);
     final data = List.generate(
-        header.numTables,
-        (i) => CmapData.fromByteData(
-            byteData, entry.offset + header.encodingRecords[i].offset));
+            header.numTables,
+            (i) => CmapData.fromByteData(
+                byteData, entry.offset + header.encodingRecords[i].offset!))
+        .whereType<CmapData>()
+        .toList();
 
     return CharacterToGlyphTable(entry, header, data);
   }
 
   factory CharacterToGlyphTable.create(List<GenericGlyph> fullGlyphList) {
-    final charCodeList = fullGlyphList.map((e) => e.metadata.charCode).toList()
-      ..removeAt(0); // removing .notdef
+    final fullCharCodeList = fullGlyphList
+        .map((e) => e.metadata.charCode)
+        .toList()
+          ..removeAt(0); // removing .notdef
+    final charCodeList = fullCharCodeList.whereType<int>().toList();
 
     final segmentList = _generateSegments(charCodeList);
     final segmentListFormat4 = [
@@ -493,7 +498,7 @@ class CharacterToGlyphTable extends FontTable {
 
     final subtableByFormat = _kDefaultEncodingRecordFormatList
         .toSet()
-        .fold<Map<int, CmapData>>({}, (p, format) {
+        .fold<Map<int, CmapData?>>({}, (p, format) {
       p[format] = CmapData.create(
           format == _kFormat4 ? segmentListFormat4 : segmentList, format);
       return p;
@@ -501,7 +506,7 @@ class CharacterToGlyphTable extends FontTable {
 
     final subtables = [
       for (final format in _kDefaultEncodingRecordFormatList)
-        subtableByFormat[format]
+        if (subtableByFormat[format] != null) subtableByFormat[format]!,
     ];
 
     final header = CharacterToGlyphTableHeader(
diff --git a/lib/src/otf/table/coverage.dart b/lib/src/otf/table/coverage.dart
index a872330..48b2ebb 100644
--- a/lib/src/otf/table/coverage.dart
+++ b/lib/src/otf/table/coverage.dart
@@ -8,7 +8,7 @@ const kDefaultCoverageTable = CoverageTableFormat1(1, 0, []);
 abstract class CoverageTable implements BinaryCodable {
   const CoverageTable();
 
-  factory CoverageTable.fromByteData(ByteData byteData, int offset) {
+  static CoverageTable? fromByteData(ByteData byteData, int offset) {
     final format = byteData.getUint16(offset);
 
     switch (format) {
diff --git a/lib/src/otf/table/feature_list.dart b/lib/src/otf/table/feature_list.dart
index 32e24d7..a418716 100644
--- a/lib/src/otf/table/feature_list.dart
+++ b/lib/src/otf/table/feature_list.dart
@@ -24,7 +24,7 @@ class FeatureRecord implements BinaryCodable {
   }
 
   final String featureTag;
-  int featureOffset;
+  int? featureOffset;
 
   @override
   int get size => kFeatureRecordSize;
@@ -33,7 +33,7 @@ class FeatureRecord implements BinaryCodable {
   void encodeToBinary(ByteData byteData) {
     byteData
       ..setTag(0, featureTag)
-      ..setUint16(4, featureOffset);
+      ..setUint16(4, featureOffset!);
   }
 }
 
@@ -43,7 +43,7 @@ class FeatureTable implements BinaryCodable {
 
   factory FeatureTable.fromByteData(
       ByteData byteData, int offset, FeatureRecord record) {
-    offset += record.featureOffset;
+    offset += record.featureOffset!;
 
     final lookupIndexCount = byteData.getUint16(offset + 2);
     final lookupListIndices = List.generate(
diff --git a/lib/src/otf/table/glyf.dart b/lib/src/otf/table/glyf.dart
index 82eefdb..07e41ac 100644
--- a/lib/src/otf/table/glyf.dart
+++ b/lib/src/otf/table/glyf.dart
@@ -12,7 +12,7 @@ import 'table_record_entry.dart';
 
 class GlyphDataTable extends FontTable {
   GlyphDataTable(
-    TableRecordEntry entry,
+    TableRecordEntry? entry,
     this.glyphList,
   ) : super.fromTableRecordEntry(entry);
 
diff --git a/lib/src/otf/table/glyph/flag.dart b/lib/src/otf/table/glyph/flag.dart
index d262cd3..2360232 100644
--- a/lib/src/otf/table/glyph/flag.dart
+++ b/lib/src/otf/table/glyph/flag.dart
@@ -23,7 +23,7 @@ class SimpleGlyphFlag implements BinaryCodable {
       this.overlapSimple,
       this.reserved);
 
-  factory SimpleGlyphFlag.fromIntValue(int flag, [int repeatTimes]) {
+  factory SimpleGlyphFlag.fromIntValue(int flag, [int? repeatTimes]) {
     return SimpleGlyphFlag(
         checkBitMask(flag, _kOnCurvePointValue),
         checkBitMask(flag, _kXshortVectorValue),
@@ -61,7 +61,7 @@ class SimpleGlyphFlag implements BinaryCodable {
   final bool onCurvePoint;
   final bool xShortVector;
   final bool yShortVector;
-  final int repeat;
+  final int? repeat;
   final bool xIsSameOrPositive;
   final bool yIsSameOrPositive;
   final bool overlapSimple;
diff --git a/lib/src/otf/table/gsub.dart b/lib/src/otf/table/gsub.dart
index 69927bb..503fac6 100644
--- a/lib/src/otf/table/gsub.dart
+++ b/lib/src/otf/table/gsub.dart
@@ -48,10 +48,10 @@ class GlyphSubstitutionTableHeader implements BinaryCodable {
 
   final int majorVersion;
   final int minorVersion;
-  int scriptListOffset;
-  int featureListOffset;
-  int lookupListOffset;
-  int featureVariationsOffset;
+  int? scriptListOffset;
+  int? featureListOffset;
+  int? lookupListOffset;
+  int? featureVariationsOffset;
 
   bool get isV10 => majorVersion == 1 && minorVersion == 0;
 
@@ -63,9 +63,9 @@ class GlyphSubstitutionTableHeader implements BinaryCodable {
     byteData
       ..setUint16(0, majorVersion)
       ..setUint16(2, minorVersion)
-      ..setUint16(4, scriptListOffset)
-      ..setUint16(6, featureListOffset)
-      ..setUint16(8, lookupListOffset);
+      ..setUint16(4, scriptListOffset!)
+      ..setUint16(6, featureListOffset!)
+      ..setUint16(8, lookupListOffset!);
 
     if (!isV10) {
       byteData.getUint32(10);
@@ -74,7 +74,7 @@ class GlyphSubstitutionTableHeader implements BinaryCodable {
 }
 
 class GlyphSubstitutionTable extends FontTable {
-  GlyphSubstitutionTable(TableRecordEntry entry, this.header,
+  GlyphSubstitutionTable(TableRecordEntry? entry, this.header,
       this.scriptListTable, this.featureListTable, this.lookupListTable)
       : super.fromTableRecordEntry(entry);
 
@@ -85,11 +85,11 @@ class GlyphSubstitutionTable extends FontTable {
     final header = GlyphSubstitutionTableHeader.fromByteData(byteData, entry);
 
     final scriptListTable = ScriptListTable.fromByteData(
-        byteData, entry.offset + header.scriptListOffset);
+        byteData, entry.offset + header.scriptListOffset!);
     final featureListTable = FeatureListTable.fromByteData(
-        byteData, entry.offset + header.featureListOffset);
+        byteData, entry.offset + header.featureListOffset!);
     final lookupListTable = LookupListTable.fromByteData(
-        byteData, entry.offset + header.lookupListOffset);
+        byteData, entry.offset + header.lookupListOffset!);
 
     return GlyphSubstitutionTable(
       entry,
diff --git a/lib/src/otf/table/head.dart b/lib/src/otf/table/head.dart
index 98d7a56..5451c30 100644
--- a/lib/src/otf/table/head.dart
+++ b/lib/src/otf/table/head.dart
@@ -2,7 +2,6 @@ import 'dart:math' as math;
 import 'dart:typed_data';
 
 import '../../common/generic_glyph.dart';
-import '../../utils/exception.dart';
 import '../../utils/misc.dart';
 import '../../utils/otf.dart';
 
@@ -23,7 +22,7 @@ const _kHeaderTableSize = 54;
 
 class HeaderTable extends FontTable {
   HeaderTable(
-      TableRecordEntry entry,
+      TableRecordEntry? entry,
       this.fontRevision,
       this.checkSumAdjustment,
       this.flags,
@@ -90,15 +89,10 @@ class HeaderTable extends FontTable {
 
   factory HeaderTable.create(
     List<GenericGlyphMetrics> glyphMetricsList,
-    GlyphDataTable glyf,
+    GlyphDataTable? glyf,
     Revision revision,
     int unitsPerEm,
   ) {
-    if (revision == null || revision.int32value == 0) {
-      throw TableDataFormatException('revision must not be null');
-    }
-
-    final isOpenType = glyf == null;
     final now = MockableDateTime.now();
 
     final xMin = glyphMetricsList.fold<int>(
@@ -124,7 +118,7 @@ class HeaderTable extends FontTable {
         yMax,
         _kMacStyleRegular,
         _kLowestRecPPEMdefault,
-        isOpenType || glyf.size < 0x20000
+        glyf == null || glyf.size < 0x20000
             ? _kIndexToLocFormatShort
             : _kIndexToLocFormatLong);
   }
diff --git a/lib/src/otf/table/hhea.dart b/lib/src/otf/table/hhea.dart
index b26ed76..c8b5ff9 100644
--- a/lib/src/otf/table/hhea.dart
+++ b/lib/src/otf/table/hhea.dart
@@ -10,7 +10,7 @@ const _kHheaTableSize = 36;
 
 class HorizontalHeaderTable extends FontTable {
   HorizontalHeaderTable(
-    TableRecordEntry entry,
+    TableRecordEntry? entry,
     this.majorVersion,
     this.minorVersion,
     this.ascender,
diff --git a/lib/src/otf/table/hmtx.dart b/lib/src/otf/table/hmtx.dart
index a3888f4..0878398 100644
--- a/lib/src/otf/table/hmtx.dart
+++ b/lib/src/otf/table/hmtx.dart
@@ -49,7 +49,7 @@ class LongHorMetric implements BinaryCodable {
 
 class HorizontalMetricsTable extends FontTable {
   HorizontalMetricsTable(
-    TableRecordEntry entry,
+    TableRecordEntry? entry,
     this.hMetrics,
     this.leftSideBearings,
   ) : super.fromTableRecordEntry(entry);
diff --git a/lib/src/otf/table/loca.dart b/lib/src/otf/table/loca.dart
index 32f6649..cc91016 100644
--- a/lib/src/otf/table/loca.dart
+++ b/lib/src/otf/table/loca.dart
@@ -7,7 +7,7 @@ import 'table_record_entry.dart';
 
 class IndexToLocationTable extends FontTable {
   IndexToLocationTable(
-    TableRecordEntry entry,
+    TableRecordEntry? entry,
     this.glyphOffsets,
     this._isShort,
   ) : super.fromTableRecordEntry(entry);
diff --git a/lib/src/otf/table/lookup.dart b/lib/src/otf/table/lookup.dart
index 9883b64..336f6d8 100644
--- a/lib/src/otf/table/lookup.dart
+++ b/lib/src/otf/table/lookup.dart
@@ -18,7 +18,7 @@ const _kDefaultLookupTableList = [
 abstract class SubstitutionSubtable implements BinaryCodable {
   const SubstitutionSubtable();
 
-  factory SubstitutionSubtable.fromByteData(
+  static SubstitutionSubtable? fromByteData(
       ByteData byteData, int offset, int lookupType) {
     switch (lookupType) {
       case 4:
@@ -65,10 +65,10 @@ class LigatureSubstitutionSubtable extends SubstitutionSubtable {
   final int ligatureSetCount;
   final List<int> ligatureSetOffsets;
 
-  final CoverageTable coverageTable;
+  final CoverageTable? coverageTable;
 
   @override
-  int get size => 6 + 2 * ligatureSetCount + coverageTable.size;
+  int get size => 6 + 2 * ligatureSetCount + (coverageTable?.size ?? 0);
 
   /// NOTE: Should be calculated considering 'componentCount' of ligatures.
   ///
@@ -89,8 +89,8 @@ class LigatureSubstitutionSubtable extends SubstitutionSubtable {
       byteData.setInt16(6 + 2 * i, ligatureSetOffsets[i]);
     }
 
-    coverageTable.encodeToBinary(
-        byteData.sublistView(coverageOffset, coverageTable.size));
+    coverageTable?.encodeToBinary(
+        byteData.sublistView(coverageOffset, coverageTable!.size));
   }
 }
 
@@ -114,9 +114,11 @@ class LookupTable implements BinaryCodable {
     final markFilteringSetOffset = offset + 6 + 2 * subTableCount;
 
     final subtables = List.generate(
-        subTableCount,
-        (i) => SubstitutionSubtable.fromByteData(
-            byteData, offset + subtableOffsets[i], lookupType));
+            subTableCount,
+            (i) => SubstitutionSubtable.fromByteData(
+                byteData, offset + subtableOffsets[i], lookupType))
+        .whereType<SubstitutionSubtable>()
+        .toList();
 
     return LookupTable(
       lookupType,
@@ -132,7 +134,7 @@ class LookupTable implements BinaryCodable {
   final int lookupFlag;
   final int subTableCount;
   final List<int> subtableOffsets;
-  final int markFilteringSet;
+  final int? markFilteringSet;
 
   final List<SubstitutionSubtable> subtables;
 
@@ -170,7 +172,7 @@ class LookupTable implements BinaryCodable {
     final useMarkFilteringSet = _useMarkFilteringSet(lookupFlag);
 
     if (useMarkFilteringSet) {
-      byteData.setUint16(6 + 2 * subTableCount, markFilteringSet);
+      byteData.setUint16(6 + 2 * subTableCount, markFilteringSet!);
     }
   }
 }
diff --git a/lib/src/otf/table/maxp.dart b/lib/src/otf/table/maxp.dart
index bdbfa5c..61c6d8a 100644
--- a/lib/src/otf/table/maxp.dart
+++ b/lib/src/otf/table/maxp.dart
@@ -16,7 +16,7 @@ const _kTableSizeForVersion = {
 };
 
 class MaximumProfileTable extends FontTable {
-  MaximumProfileTable.v0(TableRecordEntry entry, this.numGlyphs)
+  MaximumProfileTable.v0(TableRecordEntry? entry, this.numGlyphs)
       : version = _kVersion0,
         maxPoints = null,
         maxContours = null,
@@ -34,7 +34,7 @@ class MaximumProfileTable extends FontTable {
         super.fromTableRecordEntry(entry);
 
   MaximumProfileTable.v1(
-      TableRecordEntry entry,
+      TableRecordEntry? entry,
       this.numGlyphs,
       this.maxPoints,
       this.maxContours,
@@ -52,7 +52,34 @@ class MaximumProfileTable extends FontTable {
       : version = _kVersion1,
         super.fromTableRecordEntry(entry);
 
-  factory MaximumProfileTable.fromByteData(
+  factory MaximumProfileTable.create(int numGlyphs, GlyphDataTable? glyf) {
+    final isOpenType = glyf == null;
+
+    if (isOpenType) {
+      return MaximumProfileTable.v0(null, numGlyphs);
+    }
+
+    return MaximumProfileTable.v1(
+        null,
+        numGlyphs,
+        glyf!.maxPoints,
+        glyf.maxContours,
+        0, // Composite glyphs are not supported
+        0, // Composite glyphs are not supported
+        2, // The twilight zone is used
+        0, // 0 max points for the twilight zone
+
+        /// Constants taken from FontForge
+        1,
+        1,
+        0,
+        64,
+        glyf.maxSizeOfInstructions,
+        0,
+        0);
+  }
+
+  static MaximumProfileTable? fromByteData(
       ByteData data, TableRecordEntry entry) {
     final version = data.getInt32(entry.offset);
 
@@ -83,51 +110,24 @@ class MaximumProfileTable extends FontTable {
     }
   }
 
-  factory MaximumProfileTable.create(int numGlyphs, GlyphDataTable glyf) {
-    final isOpenType = glyf == null;
-
-    if (isOpenType) {
-      return MaximumProfileTable.v0(null, numGlyphs);
-    }
-
-    return MaximumProfileTable.v1(
-        null,
-        numGlyphs,
-        glyf.maxPoints,
-        glyf.maxContours,
-        0, // Composite glyphs are not supported
-        0, // Composite glyphs are not supported
-        2, // The twilight zone is used
-        0, // 0 max points for the twilight zone
-
-        /// Constants taken from FontForge
-        1,
-        1,
-        0,
-        64,
-        glyf.maxSizeOfInstructions,
-        0,
-        0);
-  }
-
   // Version 0.5
   final int version;
   final int numGlyphs;
 
   // Version 1.0
-  final int maxPoints;
-  final int maxContours;
-  final int maxCompositePoints;
-  final int maxCompositeContours;
-  final int maxZones;
-  final int maxTwilightPoints;
-  final int maxStorage;
-  final int maxFunctionDefs;
-  final int maxInstructionDefs;
-  final int maxStackElements;
-  final int maxSizeOfInstructions;
-  final int maxComponentElements;
-  final int maxComponentDepth;
+  final int? maxPoints;
+  final int? maxContours;
+  final int? maxCompositePoints;
+  final int? maxCompositeContours;
+  final int? maxZones;
+  final int? maxTwilightPoints;
+  final int? maxStorage;
+  final int? maxFunctionDefs;
+  final int? maxInstructionDefs;
+  final int? maxStackElements;
+  final int? maxSizeOfInstructions;
+  final int? maxComponentElements;
+  final int? maxComponentDepth;
 
   @override
   void encodeToBinary(ByteData byteData) {
@@ -137,24 +137,24 @@ class MaximumProfileTable extends FontTable {
 
     if (version == _kVersion1) {
       byteData
-        ..setUint16(6, maxPoints)
-        ..setUint16(8, maxContours)
-        ..setUint16(10, maxCompositePoints)
-        ..setUint16(12, maxCompositeContours)
-        ..setUint16(14, maxZones)
-        ..setUint16(16, maxTwilightPoints)
-        ..setUint16(18, maxStorage)
-        ..setUint16(20, maxFunctionDefs)
-        ..setUint16(22, maxInstructionDefs)
-        ..setUint16(24, maxStackElements)
-        ..setUint16(26, maxSizeOfInstructions)
-        ..setUint16(28, maxComponentElements)
-        ..setUint16(30, maxComponentDepth);
+        ..setUint16(6, maxPoints!)
+        ..setUint16(8, maxContours!)
+        ..setUint16(10, maxCompositePoints!)
+        ..setUint16(12, maxCompositeContours!)
+        ..setUint16(14, maxZones!)
+        ..setUint16(16, maxTwilightPoints!)
+        ..setUint16(18, maxStorage!)
+        ..setUint16(20, maxFunctionDefs!)
+        ..setUint16(22, maxInstructionDefs!)
+        ..setUint16(24, maxStackElements!)
+        ..setUint16(26, maxSizeOfInstructions!)
+        ..setUint16(28, maxComponentElements!)
+        ..setUint16(30, maxComponentDepth!);
     } else if (version != _kVersion0) {
       OTFDebugger.debugUnsupportedTableVersion(kMaxpTag, version);
     }
   }
 
   @override
-  int get size => _kTableSizeForVersion[version];
+  int get size => _kTableSizeForVersion[version]!;
 }
diff --git a/lib/src/otf/table/name.dart b/lib/src/otf/table/name.dart
index 1dd0829..703e9d1 100644
--- a/lib/src/otf/table/name.dart
+++ b/lib/src/otf/table/name.dart
@@ -3,7 +3,6 @@ import 'dart:typed_data';
 import '../../common/codable/binary.dart';
 import '../../common/constant.dart';
 import '../../utils/enum_class.dart';
-import '../../utils/exception.dart';
 import '../../utils/otf.dart';
 import '../../utils/ucs2.dart';
 import '../debugger.dart';
@@ -107,9 +106,9 @@ class NameRecord implements BinaryCodable {
     this.platformID,
     this.encodingID,
     this.languageID,
-  )   : nameID = null,
-        length = null,
-        offset = null;
+  )   : nameID = -1,
+        length = -1,
+        offset = -1;
 
   factory NameRecord.fromByteData(ByteData byteData, int offset) {
     final length = byteData.getUint16(offset + 8);
@@ -133,20 +132,21 @@ class NameRecord implements BinaryCodable {
   final int offset;
 
   NameRecord copyWith({
-    int platformID,
-    int encodingID,
-    int languageID,
-    int nameID,
-    int length,
-    int offset,
+    int? platformID,
+    int? encodingID,
+    int? languageID,
+    int? nameID,
+    int? length,
+    int? offset,
   }) {
     return NameRecord(
-        this.platformID ?? platformID,
-        this.encodingID ?? encodingID,
-        this.languageID ?? languageID,
-        this.nameID ?? nameID,
-        this.length ?? length,
-        this.offset ?? offset);
+      platformID ?? this.platformID,
+      encodingID ?? this.encodingID,
+      languageID ?? this.languageID,
+      nameID ?? this.nameID,
+      length ?? this.length,
+      offset ?? this.offset,
+    );
   }
 
   @override
@@ -172,7 +172,12 @@ class NamingTableFormat0Header implements BinaryCodable {
     this.nameRecordList,
   );
 
-  factory NamingTableFormat0Header.fromByteData(
+  factory NamingTableFormat0Header.create(List<NameRecord> nameRecordList) {
+    return NamingTableFormat0Header(_kFormat0, nameRecordList.length,
+        6 + nameRecordList.length * _kNameRecordSize, nameRecordList);
+  }
+
+  static NamingTableFormat0Header? fromByteData(
     ByteData byteData,
     TableRecordEntry entry,
   ) {
@@ -193,11 +198,6 @@ class NamingTableFormat0Header implements BinaryCodable {
     return NamingTableFormat0Header(format, count, stringOffset, nameRecord);
   }
 
-  factory NamingTableFormat0Header.create(List<NameRecord> nameRecordList) {
-    return NamingTableFormat0Header(_kFormat0, nameRecordList.length,
-        6 + nameRecordList.length * _kNameRecordSize, nameRecordList);
-  }
-
   final int format;
   final int count;
   final int stringOffset;
@@ -223,10 +223,10 @@ class NamingTableFormat0Header implements BinaryCodable {
 }
 
 abstract class NamingTable extends FontTable {
-  NamingTable.fromTableRecordEntry(TableRecordEntry entry)
+  NamingTable.fromTableRecordEntry(TableRecordEntry? entry)
       : super.fromTableRecordEntry(entry);
 
-  factory NamingTable.fromByteData(ByteData byteData, TableRecordEntry entry) {
+  static NamingTable? fromByteData(ByteData byteData, TableRecordEntry entry) {
     final format = byteData.getUint16(entry.offset);
 
     switch (format) {
@@ -238,8 +238,8 @@ abstract class NamingTable extends FontTable {
     }
   }
 
-  factory NamingTable.create(
-      String fontName, String description, Revision revision,
+  static NamingTable? create(
+      String fontName, String? description, Revision revision,
       {int format = _kFormat0}) {
     switch (format) {
       case _kFormat0:
@@ -252,40 +252,22 @@ abstract class NamingTable extends FontTable {
 
   String get familyName;
 
-  String getStringByNameId(NameID nameId);
+  String? getStringByNameId(NameID nameId);
 }
 
 class NamingTableFormat0 extends NamingTable {
   NamingTableFormat0(
-    TableRecordEntry entry,
+    TableRecordEntry? entry,
     this.header,
     this.stringList,
   ) : super.fromTableRecordEntry(entry);
 
-  factory NamingTableFormat0.fromByteData(
-      ByteData byteData, TableRecordEntry entry) {
-    final header = NamingTableFormat0Header.fromByteData(byteData, entry);
-    final storageAreaOffset = entry.offset + header.size;
-
-    final stringList = [
-      for (final record in header.nameRecordList)
-        _getDecoder(record)(List.generate(record.length,
-            (i) => byteData.getUint8(storageAreaOffset + record.offset + i)))
-    ];
-
-    return NamingTableFormat0(entry, header, stringList);
-  }
-
   factory NamingTableFormat0.create(
-      String fontName, String description, Revision revision) {
-    if (fontName?.isNotEmpty != true) {
-      throw TableDataFormatException('Font name must be not empty');
-    }
-
+      String fontName, String? description, Revision revision) {
     final now = DateTime.now();
 
     /// Values for name ids in sorted order
-    final stringForNameMap = {
+    final stringForNameMap = <NameID, String>{
       NameID.copyright: 'Copyright $kVendorName ${now.year}',
       NameID.fontFamily: fontName,
       NameID.fontSubfamily: 'Regular',
@@ -328,6 +310,25 @@ class NamingTableFormat0 extends NamingTable {
     return NamingTableFormat0(null, header, stringList);
   }
 
+  static NamingTableFormat0? fromByteData(
+      ByteData byteData, TableRecordEntry entry) {
+    final header = NamingTableFormat0Header.fromByteData(byteData, entry);
+
+    if (header == null) {
+      return null;
+    }
+
+    final storageAreaOffset = entry.offset + header.size;
+
+    final stringList = [
+      for (final record in header.nameRecordList)
+        _getDecoder(record)(List.generate(record.length,
+            (i) => byteData.getUint8(storageAreaOffset + record.offset + i)))
+    ];
+
+    return NamingTableFormat0(entry, header, stringList);
+  }
+
   final NamingTableFormat0Header header;
   final List<String> stringList;
 
@@ -356,10 +357,10 @@ class NamingTableFormat0 extends NamingTable {
   }
 
   @override
-  String get familyName => getStringByNameId(NameID.fontFamily);
+  String get familyName => getStringByNameId(NameID.fontFamily)!;
 
   @override
-  String getStringByNameId(NameID nameId) {
+  String? getStringByNameId(NameID nameId) {
     final nameID = _kNameIDmap.getValueForKey(nameId);
     final familyIndex =
         header.nameRecordList.indexWhere((e) => e.nameID == nameID);
diff --git a/lib/src/otf/table/os2.dart b/lib/src/otf/table/os2.dart
index 0a5c12a..8bc7fc4 100644
--- a/lib/src/otf/table/os2.dart
+++ b/lib/src/otf/table/os2.dart
@@ -45,7 +45,7 @@ const _kDefaultPANOSE = [2, 0, 5, 3, 0, 0, 0, 0, 0, 0];
 
 class OS2Table extends FontTable {
   OS2Table._(
-    TableRecordEntry entry,
+    TableRecordEntry? entry,
     this.version,
     this.xAvgCharWidth,
     this.usWeightClass,
@@ -151,9 +151,9 @@ class OS2Table extends FontTable {
     String achVendID, {
     int version = _kVersion5,
   }) {
-    final asciiAchVendID = achVendID?.getAsciiPrintable();
+    final asciiAchVendID = achVendID.getAsciiPrintable();
 
-    if (asciiAchVendID?.length != 4) {
+    if (asciiAchVendID.length != 4) {
       throw TableDataFormatException(
           'Incorrect achVendID tag format in OS/2 table');
     }
@@ -263,19 +263,19 @@ class OS2Table extends FontTable {
   final int usWinDescent;
 
   // Version 1
-  final int ulCodePageRange1;
-  final int ulCodePageRange2;
+  final int? ulCodePageRange1;
+  final int? ulCodePageRange2;
 
   // Version 4
-  final int sxHeight;
-  final int sCapHeight;
-  final int usDefaultChar;
-  final int usBreakChar;
-  final int usMaxContext;
+  final int? sxHeight;
+  final int? sCapHeight;
+  final int? usDefaultChar;
+  final int? usBreakChar;
+  final int? usMaxContext;
 
   // Version 5
-  final int usLowerOpticalPointSize;
-  final int usUpperOpticalPointSize;
+  final int? usLowerOpticalPointSize;
+  final int? usUpperOpticalPointSize;
 
   @override
   int get size {
@@ -367,23 +367,23 @@ class OS2Table extends FontTable {
 
     if (isV1) {
       byteData
-        ..setUint32(78, ulCodePageRange1)
-        ..setUint32(82, ulCodePageRange2);
+        ..setUint32(78, ulCodePageRange1!)
+        ..setUint32(82, ulCodePageRange2!);
     }
 
     if (isV4) {
       byteData
-        ..setInt16(86, sxHeight)
-        ..setInt16(88, sCapHeight)
-        ..setUint16(90, usDefaultChar)
-        ..setUint16(92, usBreakChar)
-        ..setUint16(94, usMaxContext);
+        ..setInt16(86, sxHeight!)
+        ..setInt16(88, sCapHeight!)
+        ..setUint16(90, usDefaultChar!)
+        ..setUint16(92, usBreakChar!)
+        ..setUint16(94, usMaxContext!);
     }
 
     if (isV5) {
       byteData
-        ..setUint16(96, usLowerOpticalPointSize)
-        ..setUint16(98, usUpperOpticalPointSize);
+        ..setUint16(96, usLowerOpticalPointSize!)
+        ..setUint16(98, usUpperOpticalPointSize!);
     }
   }
 }
diff --git a/lib/src/otf/table/post.dart b/lib/src/otf/table/post.dart
index a4a4d48..a5159af 100644
--- a/lib/src/otf/table/post.dart
+++ b/lib/src/otf/table/post.dart
@@ -89,7 +89,7 @@ class PostScriptTableHeader implements BinaryCodable {
 abstract class PostScriptData implements BinaryCodable {
   PostScriptData();
 
-  factory PostScriptData.fromByteData(
+  static PostScriptData? fromByteData(
       ByteData byteData, int offset, PostScriptTableHeader header) {
     final version = header.version.int32value;
 
@@ -217,7 +217,7 @@ class PostScriptVersion20 extends PostScriptData {
 }
 
 class PostScriptTable extends FontTable {
-  PostScriptTable(TableRecordEntry entry, this.header, this.data)
+  PostScriptTable(TableRecordEntry? entry, this.header, this.data)
       : super.fromTableRecordEntry(entry);
 
   factory PostScriptTable.fromByteData(
@@ -247,15 +247,15 @@ class PostScriptTable extends FontTable {
   }
 
   final PostScriptTableHeader header;
-  final PostScriptData data;
+  final PostScriptData? data;
 
   @override
-  int get size => header.size + data.size;
+  int get size => header.size + (data?.size ?? 0);
 
   @override
   void encodeToBinary(ByteData byteData) {
     header.encodeToBinary(byteData);
-    data.encodeToBinary(byteData.sublistView(header.size, data.size));
+    data?.encodeToBinary(byteData.sublistView(header.size, data!.size));
   }
 }
 
diff --git a/lib/src/otf/table/script_list.dart b/lib/src/otf/table/script_list.dart
index e63b79c..519ff4e 100644
--- a/lib/src/otf/table/script_list.dart
+++ b/lib/src/otf/table/script_list.dart
@@ -34,7 +34,7 @@ class ScriptRecord implements BinaryCodable {
   }
 
   final String scriptTag;
-  int scriptOffset;
+  int? scriptOffset;
 
   @override
   int get size => kScriptRecordSize;
@@ -43,7 +43,7 @@ class ScriptRecord implements BinaryCodable {
   void encodeToBinary(ByteData byteData) {
     byteData
       ..setTag(0, scriptTag)
-      ..setUint16(4, scriptOffset);
+      ..setUint16(4, scriptOffset!);
   }
 }
 
@@ -58,10 +58,10 @@ class ScriptTable implements BinaryCodable {
 
   factory ScriptTable.fromByteData(
       ByteData byteData, int offset, ScriptRecord record) {
-    offset += record.scriptOffset;
+    offset += record.scriptOffset!;
 
     final defaultLangSysOffset = byteData.getUint16(offset);
-    LanguageSystemTable defaultLangSys;
+    LanguageSystemTable? defaultLangSys;
     if (defaultLangSysOffset != 0) {
       defaultLangSys = LanguageSystemTable.fromByteData(
           byteData, offset + defaultLangSysOffset);
@@ -91,7 +91,7 @@ class ScriptTable implements BinaryCodable {
   final List<LanguageSystemRecord> langSysRecords;
 
   final List<LanguageSystemTable> langSysTables;
-  final LanguageSystemTable defaultLangSys;
+  final LanguageSystemTable? defaultLangSys;
 
   @override
   int get size {
@@ -125,8 +125,8 @@ class ScriptTable implements BinaryCodable {
     final defaultRelativeLangSysOffset = tableRelativeOffset;
     byteData.setUint16(0, defaultRelativeLangSysOffset);
 
-    defaultLangSys.encodeToBinary(byteData.sublistView(
-        defaultRelativeLangSysOffset, defaultLangSys.size));
+    defaultLangSys?.encodeToBinary(byteData.sublistView(
+        defaultRelativeLangSysOffset, defaultLangSys!.size));
   }
 }
 
diff --git a/lib/src/svg/element.dart b/lib/src/svg/element.dart
index ca974f8..13f676c 100644
--- a/lib/src/svg/element.dart
+++ b/lib/src/svg/element.dart
@@ -4,13 +4,14 @@ import 'package:xml/xml.dart';
 import '../utils/svg.dart';
 import 'path.dart';
 import 'shapes.dart';
+import 'unknown_element.dart';
 
 abstract class SvgElement {
-  SvgElement(this.parent, this.xmlElement, {Matrix3 transform})
+  SvgElement(this.parent, this.xmlElement, {Matrix3? transform})
       : transform = transform ?? xmlElement?.parseTransformMatrix();
 
   factory SvgElement.fromXmlElement(
-      SvgElement parent, XmlElement element, bool ignoreShapes) {
+      SvgElement? parent, XmlElement element, bool ignoreShapes) {
     switch (element.name.local) {
       case 'path':
         return PathElement.fromXmlElement(parent, element);
@@ -28,25 +29,25 @@ abstract class SvgElement {
         return LineElement.fromXmlElement(parent, element);
     }
 
-    return null;
+    return UnknownElement(parent, element);
   }
 
-  final XmlElement xmlElement;
-  Matrix3 transform;
-  SvgElement parent;
-
-  bool get hasTransform => transform != null && !transform.isIdentity();
+  final XmlElement? xmlElement;
+  Matrix3? transform;
+  SvgElement? parent;
 
   /// Traverses parent elements and calculates result transform matrix.
   ///
   /// Returns result transform matrix or null, if there are no transforms.
-  Matrix3 getResultTransformMatrix() {
+  Matrix3? getResultTransformMatrix() {
     final transform = Matrix3.identity();
-    var element = this;
+    SvgElement? element = this;
 
     while (element != null) {
-      if (element.hasTransform) {
-        transform.multiply(element.transform);
+      final elementTransform = element.transform;
+
+      if (elementTransform != null) {
+        transform.multiply(elementTransform);
       }
 
       element = element.parent;
@@ -57,11 +58,11 @@ abstract class SvgElement {
 }
 
 class GroupElement extends SvgElement {
-  GroupElement(this.elementList, SvgElement parent, XmlElement element)
+  GroupElement(this.elementList, SvgElement? parent, XmlElement element)
       : super(parent, element);
 
   factory GroupElement.fromXmlElement(
-    SvgElement parent,
+    SvgElement? parent,
     XmlElement element,
     bool ignoreShapes,
   ) {
@@ -88,7 +89,7 @@ class GroupElement extends SvgElement {
 
     for (final c in elementList) {
       c.transform ??= Matrix3.identity();
-      c.transform.multiply(transform);
+      c.transform!.multiply(transform!);
     }
 
     transform = null;
diff --git a/lib/src/svg/path.dart b/lib/src/svg/path.dart
index 7f4fc41..546decc 100644
--- a/lib/src/svg/path.dart
+++ b/lib/src/svg/path.dart
@@ -5,11 +5,11 @@ import '../utils/exception.dart';
 import 'element.dart';
 
 class PathElement extends SvgElement {
-  PathElement(this.fillRule, this.data, SvgElement parent, XmlElement element,
-      {Matrix3 transform})
+  PathElement(this.fillRule, this.data, SvgElement? parent, XmlElement? element,
+      {Matrix3? transform})
       : super(parent, element, transform: transform);
 
-  factory PathElement.fromXmlElement(SvgElement parent, XmlElement element) {
+  factory PathElement.fromXmlElement(SvgElement? parent, XmlElement element) {
     final dAttr = element.getAttribute('d');
 
     if (dAttr == null) {
@@ -21,6 +21,6 @@ class PathElement extends SvgElement {
     return PathElement(fillRule, dAttr, parent, element);
   }
 
-  final String fillRule;
+  final String? fillRule;
   final String data;
 }
diff --git a/lib/src/svg/shapes.dart b/lib/src/svg/shapes.dart
index 0d83ca5..fdf0de2 100644
--- a/lib/src/svg/shapes.dart
+++ b/lib/src/svg/shapes.dart
@@ -13,15 +13,15 @@ abstract class PathConvertible {
 
 class RectElement extends SvgElement implements PathConvertible {
   RectElement(
-      this.rectangle, this.rx, this.ry, SvgElement parent, XmlElement element)
+      this.rectangle, this.rx, this.ry, SvgElement? parent, XmlElement element)
       : super(parent, element);
 
-  factory RectElement.fromXmlElement(SvgElement parent, XmlElement element) {
+  factory RectElement.fromXmlElement(SvgElement? parent, XmlElement element) {
     final rect = math.Rectangle(
-      element.getScalarAttribute('x'),
-      element.getScalarAttribute('y'),
-      element.getScalarAttribute('width'),
-      element.getScalarAttribute('height'),
+      element.getScalarAttribute('x')!,
+      element.getScalarAttribute('y')!,
+      element.getScalarAttribute('width')!,
+      element.getScalarAttribute('height')!,
     );
 
     var rx = element.getScalarAttribute('rx', zeroIfAbsent: false);
@@ -61,14 +61,14 @@ class RectElement extends SvgElement implements PathConvertible {
 }
 
 class CircleElement extends SvgElement implements PathConvertible {
-  CircleElement(this.center, this.r, SvgElement parent, XmlElement element)
+  CircleElement(this.center, this.r, SvgElement? parent, XmlElement element)
       : super(parent, element);
 
-  factory CircleElement.fromXmlElement(SvgElement parent, XmlElement element) {
+  factory CircleElement.fromXmlElement(SvgElement? parent, XmlElement element) {
     final center = math.Point(
-        element.getScalarAttribute('cx'), element.getScalarAttribute('cy'));
+        element.getScalarAttribute('cx')!, element.getScalarAttribute('cy')!);
 
-    final r = element.getScalarAttribute('r');
+    final r = element.getScalarAttribute('r')!;
 
     return CircleElement(center, r, parent, element);
   }
@@ -90,12 +90,12 @@ class CircleElement extends SvgElement implements PathConvertible {
 }
 
 class PolylineElement extends SvgElement implements PathConvertible {
-  PolylineElement(this.points, SvgElement parent, XmlElement element)
+  PolylineElement(this.points, SvgElement? parent, XmlElement element)
       : super(parent, element);
 
   factory PolylineElement.fromXmlElement(
-      SvgElement parent, XmlElement element) {
-    final points = element.getAttribute('points');
+      SvgElement? parent, XmlElement element) {
+    final points = element.getAttribute('points')!;
 
     return PolylineElement(points, parent, element);
   }
@@ -111,11 +111,12 @@ class PolylineElement extends SvgElement implements PathConvertible {
 }
 
 class PolygonElement extends SvgElement implements PathConvertible {
-  PolygonElement(this.points, SvgElement parent, XmlElement element)
+  PolygonElement(this.points, SvgElement? parent, XmlElement element)
       : super(parent, element);
 
-  factory PolygonElement.fromXmlElement(SvgElement parent, XmlElement element) {
-    final points = element.getAttribute('points');
+  factory PolygonElement.fromXmlElement(
+      SvgElement? parent, XmlElement element) {
+    final points = element.getAttribute('points')!;
 
     return PolygonElement(points, parent, element);
   }
@@ -131,15 +132,15 @@ class PolygonElement extends SvgElement implements PathConvertible {
 }
 
 class LineElement extends SvgElement implements PathConvertible {
-  LineElement(this.p1, this.p2, SvgElement parent, XmlElement element)
+  LineElement(this.p1, this.p2, SvgElement? parent, XmlElement element)
       : super(parent, element);
 
-  factory LineElement.fromXmlElement(SvgElement parent, XmlElement element) {
+  factory LineElement.fromXmlElement(SvgElement? parent, XmlElement element) {
     final p1 = math.Point(
-        element.getScalarAttribute('x1'), element.getScalarAttribute('y1'));
+        element.getScalarAttribute('x1')!, element.getScalarAttribute('y1')!);
 
     final p2 = math.Point(
-        element.getScalarAttribute('x2'), element.getScalarAttribute('y2'));
+        element.getScalarAttribute('x2')!, element.getScalarAttribute('y2')!);
 
     return LineElement(p1, p2, parent, element);
   }
diff --git a/lib/src/svg/svg.dart b/lib/src/svg/svg.dart
index 98ee2e8..e4942d3 100644
--- a/lib/src/svg/svg.dart
+++ b/lib/src/svg/svg.dart
@@ -24,7 +24,7 @@ class Svg extends SvgElement {
   ///
   /// Throws [XmlParserException] if XML parsing exception occurs.
   /// Throws [SvgParserException] on any problem related to SVG parsing.
-  factory Svg.parse(String name, String xmlString, {bool ignoreShapes}) {
+  factory Svg.parse(String name, String xmlString, {bool? ignoreShapes}) {
     ignoreShapes ??= true;
 
     final xml = XmlDocument.parse(xmlString);
@@ -34,12 +34,12 @@ class Svg extends SvgElement {
       throw SvgParserException('Root element must be SVG');
     }
 
-    final vb = root
+    final parsedVb = root
         .getAttribute('viewBox')
-        .split(RegExp(r'[\s|,]'))
-        .where((e) => e != null)
-        .map(num.parse)
-        .toList();
+        ?.split(RegExp(r'[\s|,]'))
+        .where((e) => e.isNotEmpty)
+        .map(num.parse);
+    final vb = [...?parsedVb];
 
     if (vb.isEmpty || vb.length > 4) {
       throw SvgParserException('viewBox must contain 1..4 parameters');
diff --git a/lib/src/svg/transform.dart b/lib/src/svg/transform.dart
index cb36ef1..b1e30ce 100644
--- a/lib/src/svg/transform.dart
+++ b/lib/src/svg/transform.dart
@@ -24,23 +24,23 @@ final _transformParameterRegExp = RegExp(r'[\w.-]+');
 class Transform {
   Transform(this.type, this.parameterList);
 
-  final TransformType type;
+  final TransformType? type;
   final List<double> parameterList;
 
-  static List<Transform> parse(String string) {
+  static List<Transform> parse(String? string) {
     if (string == null) {
       return [];
     }
 
     final transforms = _transformRegExp.allMatches(string).map((m) {
-      final name = m.group(1);
+      final name = m.group(1)!;
       final type = _kTransformNameMap.getKeyForValue(name);
 
-      final parameterString = m.group(2);
+      final parameterString = m.group(2)!;
       final parameterMatches =
           _transformParameterRegExp.allMatches(parameterString);
       final parameterList =
-          parameterMatches.map((m) => double.parse(m.group(0))).toList();
+          parameterMatches.map((m) => double.parse(m.group(0)!)).toList();
 
       return Transform(type, parameterList);
     }).toList();
@@ -48,7 +48,7 @@ class Transform {
     return transforms;
   }
 
-  Matrix3 get matrix {
+  Matrix3? get matrix {
     switch (type) {
       case TransformType.matrix:
         return Matrix3.fromList(
@@ -83,16 +83,16 @@ class Transform {
         return _skewX(parameterList[0]);
       case TransformType.skewY:
         return _skewY(parameterList[0]);
+      case null:
+        return null;
     }
-
-    return null;
   }
 }
 
 /// Generates transform matrix for a list of transforms.
 ///
 /// Returns null, if transformList is empty.
-Matrix3 generateTransformMatrix(List<Transform> transformList) {
+Matrix3? generateTransformMatrix(List<Transform> transformList) {
   if (transformList.isEmpty) {
     return null;
   }
@@ -100,7 +100,9 @@ Matrix3 generateTransformMatrix(List<Transform> transformList) {
   final matrix = Matrix3.identity();
 
   for (final t in transformList) {
-    matrix.multiply(t.matrix);
+    if (t.matrix != null) {
+      matrix.multiply(t.matrix!);
+    }
   }
 
   return matrix;
diff --git a/lib/src/svg/unknown_element.dart b/lib/src/svg/unknown_element.dart
new file mode 100644
index 0000000..6b7ce33
--- /dev/null
+++ b/lib/src/svg/unknown_element.dart
@@ -0,0 +1,8 @@
+import 'package:xml/xml.dart';
+
+import 'element.dart';
+
+class UnknownElement extends SvgElement {
+  UnknownElement(SvgElement? parent, XmlElement? element)
+      : super(parent, element);
+}
diff --git a/lib/src/utils/enum_class.dart b/lib/src/utils/enum_class.dart
index 336c608..23ecc7c 100644
--- a/lib/src/utils/enum_class.dart
+++ b/lib/src/utils/enum_class.dart
@@ -1,16 +1,18 @@
+import 'package:collection/collection.dart';
+
 class EnumClass<K, V> {
   const EnumClass(this._map);
 
   final Map<K, V> _map;
 
-  K getKeyForValue(V value) {
-    final entry = _map.entries
-        .firstWhere((entry) => entry.value == value, orElse: () => null);
+  K? getKeyForValue(V value) {
+    final entry =
+        _map.entries.firstWhereOrNull((entry) => entry.value == value);
 
     return entry?.key;
   }
 
-  V getValueForKey(K key) {
+  V? getValueForKey(K key) {
     return _map[key];
   }
 
@@ -22,5 +24,5 @@ class EnumClass<K, V> {
 
   Map<K, V> get map => _map;
 
-  V operator [](K key) => _map[key];
+  V? operator [](K key) => _map[key];
 }
diff --git a/lib/src/utils/exception.dart b/lib/src/utils/exception.dart
index 8f90303..fa0cea9 100644
--- a/lib/src/utils/exception.dart
+++ b/lib/src/utils/exception.dart
@@ -21,8 +21,8 @@ class ChecksumException implements Exception {
 class SvgParserException implements Exception {
   SvgParserException([this.message]);
 
-  final String message;
+  final String? message;
 
   @override
-  String toString() => message;
+  String toString() => 'SvgParserException($message)';
 }
diff --git a/lib/src/utils/flutter_class_gen.dart b/lib/src/utils/flutter_class_gen.dart
index eba44fc..9527e81 100644
--- a/lib/src/utils/flutter_class_gen.dart
+++ b/lib/src/utils/flutter_class_gen.dart
@@ -28,11 +28,11 @@ class FlutterClassGenerator {
   /// * [indent] is a number of spaces in leading indentation for class' members. Defaults to 2.
   FlutterClassGenerator(
     this.glyphList, {
-    String className,
-    String familyName,
-    String fontFileName,
-    String package,
-    int indent,
+    String? className,
+    String? familyName,
+    String? fontFileName,
+    String? package,
+    int? indent,
   })  : _indent = ' ' * (indent ?? _kDefaultIndent),
         _className = _getVarName(className ?? _kDefaultClassName),
         _familyName = familyName ?? kDefaultFontFamily,
@@ -45,7 +45,7 @@ class FlutterClassGenerator {
   final String _className;
   final String _familyName;
   final String _indent;
-  final String _package;
+  final String? _package;
   final List<String> _iconVarNames;
 
   static List<String> _generateVariableNames(List<GenericGlyph> glyphList) {
@@ -53,7 +53,7 @@ class FlutterClassGenerator {
 
     return glyphList.map((g) {
       final baseName =
-          _getVarName(p.basenameWithoutExtension(g.metadata.name)).snakeCase;
+          _getVarName(p.basenameWithoutExtension(g.metadata.name!)).snakeCase;
       final usingDefaultName = baseName.isEmpty;
 
       var variableName = usingDefaultName ? _kUnnamedIconName : baseName;
@@ -67,8 +67,8 @@ class FlutterClassGenerator {
         var variableWithoutCount = variableName;
 
         if (countMatch != null) {
-          variableNameCount = int.parse(countMatch.group(2));
-          variableWithoutCount = countMatch.group(1);
+          variableNameCount = int.parse(countMatch.group(2)!);
+          variableWithoutCount = countMatch.group(1)!;
         }
 
         String variableNameWithCount;
@@ -97,8 +97,8 @@ class FlutterClassGenerator {
   List<String> _generateIconConst(int index) {
     final glyphMeta = glyphList[index].metadata;
 
-    final charCode = glyphMeta.charCode;
-    final iconName = glyphMeta.name;
+    final charCode = glyphMeta.charCode!;
+    final iconName = glyphMeta.name!;
 
     final varName = _iconVarNames[index];
     final hexCode = charCode.toRadixString(16);
diff --git a/lib/src/utils/misc.dart b/lib/src/utils/misc.dart
index a2793da..181b766 100644
--- a/lib/src/utils/misc.dart
+++ b/lib/src/utils/misc.dart
@@ -30,7 +30,7 @@ List<math.Point<num>> quadCurveToCubic(
 }
 
 extension MockableDateTime on DateTime {
-  static DateTime mockedDate;
+  static DateTime? mockedDate;
 
   static DateTime now() => mockedDate ?? DateTime.now();
 }
diff --git a/lib/src/utils/otf.dart b/lib/src/utils/otf.dart
index bbe207c..c5339ef 100644
--- a/lib/src/utils/otf.dart
+++ b/lib/src/utils/otf.dart
@@ -151,7 +151,7 @@ extension OTFByteDateExt on ByteData {
     setInt64(offset, dateTime.difference(_longDateTimeStart).inSeconds);
   }
 
-  ByteData sublistView(int offset, [int length]) {
+  ByteData sublistView(int offset, [int? length]) {
     return ByteData.sublistView(
         this, offset, length == null ? null : offset + length);
   }
@@ -169,7 +169,7 @@ extension OTFStringExt on String {
 
 @immutable
 class Revision {
-  const Revision(int major, int minor)
+  const Revision(int? major, int? minor)
       : major = major ?? 0,
         minor = minor ?? 0;
 
diff --git a/lib/src/utils/svg.dart b/lib/src/utils/svg.dart
index 9a632f6..e5b0406 100644
--- a/lib/src/utils/svg.dart
+++ b/lib/src/utils/svg.dart
@@ -4,10 +4,11 @@ import 'package:xml/xml.dart';
 import '../svg/element.dart';
 import '../svg/shapes.dart';
 import '../svg/transform.dart';
+import '../svg/unknown_element.dart';
 
 extension XmlElementExt on XmlElement {
-  num getScalarAttribute(String name,
-      {String namespace, bool zeroIfAbsent = true}) {
+  num? getScalarAttribute(String name,
+      {String? namespace, bool zeroIfAbsent = true}) {
     final attr = getAttribute(name, namespace: namespace);
 
     if (attr == null) {
@@ -17,21 +18,20 @@ extension XmlElementExt on XmlElement {
     return num.parse(attr);
   }
 
-  List<SvgElement> parseSvgElements(SvgElement parent, bool ignoreShapes) {
+  List<SvgElement> parseSvgElements(SvgElement? parent, bool ignoreShapes) {
     var elements = children
         .whereType<XmlElement>()
         .map((e) => SvgElement.fromXmlElement(parent, e, ignoreShapes))
         // Ignoring unknown elements
-        .where((e) => e != null)
+        .where((e) => e is! UnknownElement)
         // Expanding groups
         .expand((e) {
       if (e is! GroupElement) {
         return [e];
       }
 
-      final g = e as GroupElement..applyTransformOnChildren();
-
-      return g.elementList;
+      e.applyTransformOnChildren();
+      return e.elementList;
     });
 
     if (!ignoreShapes) {
@@ -43,7 +43,7 @@ extension XmlElementExt on XmlElement {
     return elements.toList();
   }
 
-  Matrix3 parseTransformMatrix() {
+  Matrix3? parseTransformMatrix() {
     final transformList = Transform.parse(getAttribute('transform'));
     return generateTransformMatrix(transformList);
   }
diff --git a/pubspec.yaml b/pubspec.yaml
index 61fa050..b64ecc5 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,27 +1,28 @@
 name: fontify
-version: 0.2.0
+version: 0.3.0-nullsafety.0
 description: >-
   Converts SVG icons to OTF font and generates Flutter-compatible class.
   Provides an API and a CLI tool.
 homepage: https://github.com/westracer/fontify
 
 environment:
-  sdk: ">=2.6.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
-  meta: ^1.1.8
-  xml: ^4.2.0
-  path: ^1.7.0
-  path_parsing: ^0.1.4
-  vector_math: ^2.0.8
-  logger: ^0.9.1
-  recase: ^3.0.0
-  args: ^1.6.0
-  yaml: ^2.2.1
+  args: ^2.0.0
+  collection: ^1.15.0
+  logger: ^1.0.0
+  meta: ^1.3.0
+  path: ^1.8.0
+  path_parsing: ^0.2.0
+  recase: ^4.0.0
+  vector_math: ^2.1.0
+  xml: ^5.1.0
+  yaml: ^3.1.0
 
 dev_dependencies:
-  pedantic: ^1.9.0
-  test: ^1.14.7
+  pedantic: ^1.11.0
+  test: ^1.17.0
   
 executables:
   fontify: fontify
\ No newline at end of file
diff --git a/test/assets/test_config.yaml b/test/assets/test_config.yaml
index e51c42b..ccd015c 100644
--- a/test/assets/test_config.yaml
+++ b/test/assets/test_config.yaml
@@ -15,4 +15,8 @@ fontify:
   ignore_shapes: false
 
   recursive: false
-  verbose: false
\ No newline at end of file
+  verbose: false
+
+  # Unknown config parameters
+  testing: true
+  1: 1
\ No newline at end of file
diff --git a/test/cli_test.dart b/test/cli_test.dart
index 74b4826..d47039d 100644
--- a/test/cli_test.dart
+++ b/test/cli_test.dart
@@ -9,7 +9,7 @@ void main() {
     defineOptions(_argParser);
 
     void expectCliArgumentException(List<String> args) {
-      expect(() => parseArguments(_argParser, args).validate(),
+      expect(() => parseArguments(_argParser, args),
           throwsA(const TypeMatcher<CliArgumentException>()));
     }
 
@@ -51,11 +51,11 @@ void main() {
         '--package=test_package',
       ];
 
-      final parsedArgs = parseArguments(_argParser, args)..validate();
+      final parsedArgs = parseArguments(_argParser, args);
 
       expect(parsedArgs.svgDir.path, args.first);
       expect(parsedArgs.fontFile.path, args[1]);
-      expect(parsedArgs.classFile.path, 'test/a/df.dart');
+      expect(parsedArgs.classFile?.path, 'test/a/df.dart');
       expect(parsedArgs.indent, 4);
       expect(parsedArgs.className, 'MyIcons');
       expect(parsedArgs.fontName, 'My Icons');
@@ -63,7 +63,7 @@ void main() {
       expect(parsedArgs.ignoreShapes, isFalse);
       expect(parsedArgs.recursive, isTrue);
       expect(parsedArgs.verbose, isTrue);
-      expect(parsedArgs.configFile.path, 'test/config.yaml');
+      expect(parsedArgs.configFile?.path, 'test/config.yaml');
       expect(parsedArgs.fontPackage, 'test_package');
     });
 
@@ -75,7 +75,7 @@ void main() {
         '--ignore-shapes',
       ];
 
-      final parsedArgs = parseArguments(_argParser, args)..validate();
+      final parsedArgs = parseArguments(_argParser, args);
 
       expect(parsedArgs.svgDir.path, args.first);
       expect(parsedArgs.fontFile.path, args[1]);
@@ -93,7 +93,7 @@ void main() {
 
     test('Help', () {
       void expectCliHelpException(List<String> args) {
-        expect(() => parseArguments(_argParser, args).validate(),
+        expect(() => parseArguments(_argParser, args),
             throwsA(const TypeMatcher<CliHelpException>()));
       }
 
@@ -120,7 +120,7 @@ void main() {
 
     test('All arguments and config', () {
       const args = [
-        'no',
+        './',
         'no',
         '--output-class-file=no',
         '--indent=0',
@@ -134,11 +134,11 @@ void main() {
         '--config-file=test/assets/test_config.yaml',
       ];
 
-      final parsedArgs = parseArgsAndConfig(_argParser, args)..validate();
+      final parsedArgs = parseArgsAndConfig(_argParser, args);
 
       expect(parsedArgs.svgDir.path, './');
       expect(parsedArgs.fontFile.path, 'generated_font.otf');
-      expect(parsedArgs.classFile.path, 'lib/test_font.dart');
+      expect(parsedArgs.classFile?.path, 'lib/test_font.dart');
       expect(parsedArgs.indent, 4);
       expect(parsedArgs.className, 'MyIcons');
       expect(parsedArgs.fontName, 'My Icons');
@@ -152,14 +152,16 @@ void main() {
 
     test('No arguments and config', () {
       const args = [
+        './',
+        'yes',
         '--config-file=test/assets/test_config.yaml',
       ];
 
-      final parsedArgs = parseArgsAndConfig(_argParser, args)..validate();
+      final parsedArgs = parseArgsAndConfig(_argParser, args);
 
       expect(parsedArgs.svgDir.path, './');
       expect(parsedArgs.fontFile.path, 'generated_font.otf');
-      expect(parsedArgs.classFile.path, 'lib/test_font.dart');
+      expect(parsedArgs.classFile?.path, 'lib/test_font.dart');
       expect(parsedArgs.indent, 4);
       expect(parsedArgs.className, 'MyIcons');
       expect(parsedArgs.fontName, 'My Icons');
@@ -174,7 +176,7 @@ void main() {
 
   group('Config', () {
     void expectCliArgumentException(String cfg) {
-      expect(() => parseConfig(cfg).validate(),
+      expect(() => parseConfig(cfg),
           throwsA(const TypeMatcher<CliArgumentException>()));
     }
 
@@ -243,19 +245,19 @@ fontify:
 
   recursive: true
   verbose: true
-      ''')..validate();
+      ''');
 
-      expect(parsedArgs.svgDir.path, './');
-      expect(parsedArgs.fontFile.path, 'generated_font.otf');
-      expect(parsedArgs.classFile.path, 'lib/test_font.dart');
-      expect(parsedArgs.indent, 4);
-      expect(parsedArgs.className, 'MyIcons');
-      expect(parsedArgs.fontName, 'My Icons');
-      expect(parsedArgs.normalize, isFalse);
-      expect(parsedArgs.ignoreShapes, isFalse);
-      expect(parsedArgs.recursive, isTrue);
-      expect(parsedArgs.verbose, isTrue);
-      expect(parsedArgs.fontPackage, 'test_package');
+      expect(parsedArgs?.svgDir.path, './');
+      expect(parsedArgs?.fontFile.path, 'generated_font.otf');
+      expect(parsedArgs?.classFile?.path, 'lib/test_font.dart');
+      expect(parsedArgs?.indent, 4);
+      expect(parsedArgs?.className, 'MyIcons');
+      expect(parsedArgs?.fontName, 'My Icons');
+      expect(parsedArgs?.normalize, isFalse);
+      expect(parsedArgs?.ignoreShapes, isFalse);
+      expect(parsedArgs?.recursive, isTrue);
+      expect(parsedArgs?.verbose, isTrue);
+      expect(parsedArgs?.fontPackage, 'test_package');
     });
 
     test('All arguments with defaults', () {
@@ -263,19 +265,19 @@ fontify:
 fontify:
   input_svg_dir: ./
   output_font_file: generated_font.otf
-      ''')..validate();
+      ''');
 
-      expect(parsedArgs.svgDir.path, './');
-      expect(parsedArgs.fontFile.path, 'generated_font.otf');
-      expect(parsedArgs.classFile, isNull);
-      expect(parsedArgs.indent, null);
-      expect(parsedArgs.className, isNull);
-      expect(parsedArgs.fontName, isNull);
-      expect(parsedArgs.normalize, isNull);
-      expect(parsedArgs.ignoreShapes, isNull);
-      expect(parsedArgs.recursive, isNull);
-      expect(parsedArgs.verbose, isNull);
-      expect(parsedArgs.fontPackage, isNull);
+      expect(parsedArgs?.svgDir.path, './');
+      expect(parsedArgs?.fontFile.path, 'generated_font.otf');
+      expect(parsedArgs?.classFile, isNull);
+      expect(parsedArgs?.indent, null);
+      expect(parsedArgs?.className, isNull);
+      expect(parsedArgs?.fontName, isNull);
+      expect(parsedArgs?.normalize, isNull);
+      expect(parsedArgs?.ignoreShapes, isNull);
+      expect(parsedArgs?.recursive, isNull);
+      expect(parsedArgs?.verbose, isNull);
+      expect(parsedArgs?.fontPackage, isNull);
     });
 
     test('Type validation', () {
diff --git a/test/ttf_test.dart b/test/ttf_test.dart
index b19c219..de1b71a 100644
--- a/test/ttf_test.dart
+++ b/test/ttf_test.dart
@@ -18,7 +18,7 @@ const _kTestFontAssetPath = '$kTestAssetsDir/test_font.ttf';
 const _kTestCFF2fontAssetPath = '$kTestAssetsDir/test_cff2_font.otf';
 
 void main() {
-  OpenTypeFont font;
+  late OpenTypeFont font;
 
   group('Reader', () {
     setUpAll(() {
@@ -285,19 +285,19 @@ void main() {
 
       expect(scriptTable.scriptRecords[0].scriptTag, 'DFLT');
       expect(scriptTable.scriptTables[0].langSysCount, 0);
-      expect(scriptTable.scriptTables[0].defaultLangSys.featureIndexCount, 1);
-      expect(scriptTable.scriptTables[0].defaultLangSys.featureIndices, [0]);
-      expect(scriptTable.scriptTables[0].defaultLangSys.lookupOrder, 0);
+      expect(scriptTable.scriptTables[0].defaultLangSys?.featureIndexCount, 1);
+      expect(scriptTable.scriptTables[0].defaultLangSys?.featureIndices, [0]);
+      expect(scriptTable.scriptTables[0].defaultLangSys?.lookupOrder, 0);
       expect(
-          scriptTable.scriptTables[0].defaultLangSys.requiredFeatureIndex, 0);
+          scriptTable.scriptTables[0].defaultLangSys?.requiredFeatureIndex, 0);
 
       expect(scriptTable.scriptRecords[1].scriptTag, 'latn');
       expect(scriptTable.scriptTables[1].langSysCount, 0);
-      expect(scriptTable.scriptTables[1].defaultLangSys.featureIndexCount, 1);
-      expect(scriptTable.scriptTables[1].defaultLangSys.featureIndices, [0]);
-      expect(scriptTable.scriptTables[1].defaultLangSys.lookupOrder, 0);
+      expect(scriptTable.scriptTables[1].defaultLangSys?.featureIndexCount, 1);
+      expect(scriptTable.scriptTables[1].defaultLangSys?.featureIndices, [0]);
+      expect(scriptTable.scriptTables[1].defaultLangSys?.lookupOrder, 0);
       expect(
-          scriptTable.scriptTables[1].defaultLangSys.requiredFeatureIndex, 0);
+          scriptTable.scriptTables[1].defaultLangSys?.requiredFeatureIndex, 0);
 
       final featureTable = table.featureListTable;
       expect(featureTable.featureCount, 1);
@@ -328,8 +328,8 @@ void main() {
   });
 
   group('Creation & Writer', () {
-    ByteData originalByteData, recreatedByteData;
-    OpenTypeFont recreatedFont;
+    late ByteData originalByteData, recreatedByteData;
+    late OpenTypeFont recreatedFont;
 
     setUpAll(() {
       MockableDateTime.mockedDate = DateTime.utc(2020, 2, 2, 2, 2);
@@ -368,20 +368,20 @@ void main() {
       const expected =
           'AAEAAAABAADXpqNjXw889QALBAAAAAAA2lveGAAAAADaW94Y//X/ZwZkBAAAAAAIAAIAAAAA';
       final actual = base64Encode(recreatedByteData.buffer.asUint8List(
-          recreatedFont.head.entry.offset, recreatedFont.head.entry.length));
+          recreatedFont.head.entry!.offset, recreatedFont.head.entry!.length));
 
       expect(actual, expected);
-      expect(recreatedFont.head.entry.checkSum, 439353492);
+      expect(recreatedFont.head.entry!.checkSum, 439353492);
     }, skip: "Font's checksum is always changing, unskip later");
 
     test('Glyph Substitution table', () {
       const expected =
           'AAEAAAAKADAAPgACREZMVAAObGF0bgAaAAQAAAAA//8AAQAAAAQAAAAA//8AAQAAAAFsaWdhAAgAAAABAAAAAQAEAAQAAAABAAgAAQAGAAAAAQAA';
       final actual = base64Encode(recreatedByteData.buffer.asUint8List(
-          recreatedFont.gsub.entry.offset, recreatedFont.gsub.entry.length));
+          recreatedFont.gsub.entry!.offset, recreatedFont.gsub.entry!.length));
 
       expect(actual, expected);
-      expect(recreatedFont.gsub.entry.checkSum, 546121080);
+      expect(recreatedFont.gsub.entry!.checkSum, 546121080);
     });
 
     test('OS/2 V5', () {
@@ -393,7 +393,7 @@ void main() {
   });
 
   group('CFF', () {
-    ByteData byteData;
+    late ByteData byteData;
 
     setUpAll(() {
       byteData =
@@ -405,10 +405,10 @@ void main() {
       final table = font.cff2;
 
       final originalCFF2byteList =
-          byteData.buffer.asUint8List(table.entry.offset, table.size).toList();
+          byteData.buffer.asUint8List(table.entry!.offset, table.size).toList();
       final encodedCFF2byteData = ByteData(table.size);
 
-      expect(table.size, table.entry.length);
+      expect(table.size, table.entry!.length);
 
       table
         ..recalculateOffsets()