diff --git a/src/GraphQLParser.Benchmarks/BinaryTest.graphql b/src/GraphQLParser.Benchmarks/BinaryTest.graphql
new file mode 100644
index 00000000..ca03f5ab
Binary files /dev/null and b/src/GraphQLParser.Benchmarks/BinaryTest.graphql differ
diff --git a/src/GraphQLParser.Benchmarks/GraphQLParser.Benchmarks.csproj b/src/GraphQLParser.Benchmarks/GraphQLParser.Benchmarks.csproj
index f9e2b055..5eacd042 100644
--- a/src/GraphQLParser.Benchmarks/GraphQLParser.Benchmarks.csproj
+++ b/src/GraphQLParser.Benchmarks/GraphQLParser.Benchmarks.csproj
@@ -8,16 +8,26 @@
     <DisableImplicitFrameworkReferences>true</DisableImplicitFrameworkReferences>
   </PropertyGroup>
 
+  <ItemGroup>
+    <None Remove="BinaryTest.graphql" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Content Include="BinaryTest.graphql">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\GraphQLParser\GraphQLParser.csproj" />
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.10.8" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.10.14" />
   </ItemGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'net46' ">
-    <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Version="0.10.8" />
+    <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Version="0.10.14" />
   </ItemGroup>
 
 </Project>
diff --git a/src/GraphQLParser.Benchmarks/LexerBenchmark.cs b/src/GraphQLParser.Benchmarks/LexerBenchmark.cs
index dbcef69f..d0d6b8de 100644
--- a/src/GraphQLParser.Benchmarks/LexerBenchmark.cs
+++ b/src/GraphQLParser.Benchmarks/LexerBenchmark.cs
@@ -1,4 +1,6 @@
 using BenchmarkDotNet.Attributes;
+using GraphQLParser.Exceptions;
+using System.IO;
 
 namespace GraphQLParser.Benchmarks
 {
@@ -7,6 +9,7 @@ namespace GraphQLParser.Benchmarks
 #endif
     public class LexerBenchmark
     {
+        private static readonly string Binary = File.ReadAllText("BinaryTest.graphql");
         private const string KitchenSink = @"
 query queryName($foo: ComplexType, $site: Site = MOBILE) {
   whoever123is: node(id: [123, 456]) {
@@ -70,5 +73,18 @@ public void LexKitchenSink()
                 resetPosition = token.End;
             }
         }
+
+        [Benchmark]
+        public void ParseBinaryFile()
+        {
+            try
+            {
+                var parser = new Parser(new Lexer());
+                parser.Parse(new Source(Binary));
+            }
+            catch (GraphQLSyntaxErrorException)
+            {
+            }
+        }
     }
 }
diff --git a/src/GraphQLParser/AST/GraphQLListValue.cs b/src/GraphQLParser/AST/GraphQLListValue.cs
index 41c708d6..04919661 100644
--- a/src/GraphQLParser/AST/GraphQLListValue.cs
+++ b/src/GraphQLParser/AST/GraphQLListValue.cs
@@ -4,7 +4,7 @@
 
     public class GraphQLListValue : GraphQLValue
     {
-        private ASTNodeKind kindField;
+        private readonly ASTNodeKind kindField;
 
         public GraphQLListValue(ASTNodeKind kind)
         {
diff --git a/src/GraphQLParser/Exceptions/GraphQLSyntaxErrorException.cs b/src/GraphQLParser/Exceptions/GraphQLSyntaxErrorException.cs
index a6dad2b7..f47ff149 100644
--- a/src/GraphQLParser/Exceptions/GraphQLSyntaxErrorException.cs
+++ b/src/GraphQLParser/Exceptions/GraphQLSyntaxErrorException.cs
@@ -2,6 +2,7 @@
 {
     using System;
     using System.Linq;
+    using System.Text;
 
     public class GraphQLSyntaxErrorException : Exception
     {
@@ -49,13 +50,48 @@ private static string LeftPad(int length, string str)
 
         private static string ReplaceWithUnicodeRepresentation(string str)
         {
+            if (!HasReplacementCharacter(str))
+                return str;
+
+            var buffer = new StringBuilder(str.Length);
+
             foreach (var code in str)
             {
-                if (code < 0x0020 && code != 0x0009 && code != 0x000A && code != 0x000D)
-                    str = str.Replace(string.Empty + code, "\\u" + ((int)code).ToString("D4"));
+                if (IsReplacementCharacter(code))
+                {
+                    buffer.Append(GetUnicodeRepresentation(code));
+                }
+                else
+                {
+                    buffer.Append(code);
+                }
             }
 
-            return str;
+            return buffer.ToString();
+        }
+
+        private static bool HasReplacementCharacter(string str)
+        {
+            foreach (var code in str)
+            {
+                if (IsReplacementCharacter(code))
+                    return true;
+            }
+
+            return false;
+        }
+
+        private static bool IsReplacementCharacter(char code) => code < 0x0020 && code != 0x0009 && code != 0x000A && code != 0x000D;
+
+        private static string GetUnicodeRepresentation(char code)
+        {
+            switch (code)
+            {
+                case '\0':
+                    return "\\u0000";
+                default:
+                    return "\\u" + ((int)code).ToString("D4");
+            }
         }
     }
 }
\ No newline at end of file
diff --git a/src/GraphQLParser/LexerContext.cs b/src/GraphQLParser/LexerContext.cs
index 3dc2f5c5..75e7a17f 100644
--- a/src/GraphQLParser/LexerContext.cs
+++ b/src/GraphQLParser/LexerContext.cs
@@ -6,7 +6,7 @@
     public class LexerContext : IDisposable
     {
         private int currentIndex;
-        private ISource source;
+        private readonly ISource source;
 
         public LexerContext(ISource source, int index)
         {
diff --git a/src/GraphQLParser/ParserContext.cs b/src/GraphQLParser/ParserContext.cs
index 3e4e60e2..01e32030 100644
--- a/src/GraphQLParser/ParserContext.cs
+++ b/src/GraphQLParser/ParserContext.cs
@@ -689,7 +689,6 @@ private GraphQLValue ParseNameValue(bool isConstant)
                     $"Unexpected {this.currentToken}", this.source, this.currentToken.Start);
         }
 
-
         private GraphQLValue ParseObject(bool isConstant)
         {
             var comment = GetComment();