diff --git a/CHANGELOG.md b/CHANGELOG.md
index fcaa7c5..29c85d0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,12 +12,17 @@ Release notes are available on [github][notes].
 
 - [fix] Replace `assert()` with explicit `if`/`throw` in `getInt()`, `getDouble()`, and `getBool()` so null-safety checks are enforced in release builds
 - Error messages now include the variable name for easier debugging
+- [fix] `load(isOptional: true)` no longer discards successfully loaded base file when an override file is missing or empty (fixes #70, #93, #101, #125)
+- [fix] `clean()` now resets `isInitialized` to `false`, so accessing `env` after `clean()` correctly throws `NotInitializedError`
 
 ### Note on release-build behavior change
 In **debug mode**, behavior is unchanged — `AssertionError` was thrown before, `AssertionError` is thrown now.
 
 In **release mode**, calling `getInt()`, `getDouble()`, or `getBool()` with a missing variable and no fallback previously threw a `TypeError` (from the null-check operator `!`) because `assert()` was stripped. It now correctly throws `AssertionError` with a descriptive message. If your release-mode code catches `on TypeError` around these methods, update it to catch `on AssertionError` (or `on Error`) instead.
 
+### Breaking change: `clean()` now resets initialization state
+Previously, calling `clean()` only cleared the env map but left `isInitialized == true`. Now it also sets `isInitialized = false`. Code that calls `clean()` and then immediately accesses `dotenv.env` without reloading will now throw `NotInitializedError`. The fix is to call `load()` or `loadFromString()` again after `clean()`.
+
 # 6.0.0
 
 - [feat] Allow passing in override .env files on init
diff --git a/lib/src/dotenv.dart b/lib/src/dotenv.dart
index e246f17..c97635e 100644
--- a/lib/src/dotenv.dart
+++ b/lib/src/dotenv.dart
@@ -45,8 +45,11 @@ class DotEnv {
 
   bool get isInitialized => _isInitialized;
 
-  /// Clear [env]
-  void clean() => _envMap.clear();
+  /// Clear [env] and reset initialization state
+  void clean() {
+    _envMap.clear();
+    _isInitialized = false;
+  }
 
   String get(String name, {String? fallback}) {
     final value = maybeGet(name, fallback: fallback);
@@ -134,19 +137,26 @@ class DotEnv {
     Parser parser = const Parser(),
   }) async {
     clean();
-    List<String> linesFromFile;
-    List<String> linesFromOverrides;
+    List<String> linesFromFile = [];
+    List<String> linesFromOverrides = [];
+
     try {
       linesFromFile = await _getEntriesFromFile(fileName);
-      linesFromOverrides = await _getLinesFromOverride(overrideWithFiles);
     } on FileNotFoundError {
       if (!isOptional) rethrow;
-      linesFromFile = [];
-      linesFromOverrides = [];
     } on EmptyEnvFileError {
       if (!isOptional) rethrow;
-      linesFromFile = [];
-      linesFromOverrides = [];
+    }
+
+    for (final overrideFile in overrideWithFiles) {
+      try {
+        final lines = await _getEntriesFromFile(overrideFile);
+        linesFromOverrides.addAll(lines);
+      } on FileNotFoundError {
+        if (!isOptional) rethrow;
+      } on EmptyEnvFileError {
+        if (!isOptional) rethrow;
+      }
     }
 
     final linesFromMergeWith = mergeWith.entries
@@ -214,15 +224,4 @@ class DotEnv {
     }
   }
 
-  Future<List<String>> _getLinesFromOverride(List<String> overrideWith) async {
-    List<String> overrideLines = [];
-
-    for (int i = 0; i < overrideWith.length; i++) {
-      final overrideWithFile = overrideWith[i];
-      final lines = await _getEntriesFromFile(overrideWithFile);
-      overrideLines = overrideLines..addAll(lines);
-    }
-
-    return overrideLines;
-  }
 }
diff --git a/test/dotenv_test.dart b/test/dotenv_test.dart
index 0e289f9..67c3174 100644
--- a/test/dotenv_test.dart
+++ b/test/dotenv_test.dart
@@ -150,4 +150,66 @@ void main() {
               e.message.toString().contains('MISSING_VAR'))));
     });
   });
+
+  group('clean() resets initialization state', () {
+    test('after clean(), isInitialized is false', () {
+      dotenv.loadFromString(envString: 'FOO=bar');
+      expect(dotenv.isInitialized, isTrue);
+      dotenv.clean();
+      expect(dotenv.isInitialized, isFalse);
+    });
+
+    test('after clean(), accessing env throws NotInitializedError', () {
+      dotenv.loadFromString(envString: 'FOO=bar');
+      expect(dotenv.env['FOO'], 'bar');
+      dotenv.clean();
+      expect(() => dotenv.env, throwsA(isA<NotInitializedError>()));
+    });
+
+    test(
+        'loadFromString after clean() re-initializes correctly', () {
+      dotenv.loadFromString(envString: 'FOO=bar');
+      dotenv.clean();
+      dotenv.loadFromString(envString: 'BAZ=qux');
+      expect(dotenv.isInitialized, isTrue);
+      expect(dotenv.env['BAZ'], 'qux');
+      expect(dotenv.env['FOO'], isNull);
+    });
+  });
+
+  group('isOptional override loading', () {
+    test(
+        'loadFromString with valid base and empty override preserves base vars',
+        () {
+      dotenv.loadFromString(
+        envString: 'FOO=bar\nBAZ=qux',
+        overrideWith: [''],
+        isOptional: true,
+      );
+      expect(dotenv.env['FOO'], 'bar');
+      expect(dotenv.env['BAZ'], 'qux');
+    });
+
+    test('loadFromString with empty base and valid override preserves override',
+        () {
+      dotenv.loadFromString(
+        envString: '',
+        overrideWith: ['OVERRIDE_KEY=override_value'],
+        isOptional: true,
+      );
+      expect(dotenv.env['OVERRIDE_KEY'], 'override_value');
+    });
+
+    test(
+        'loadFromString with isOptional=false and empty base throws even with valid override',
+        () {
+      expect(
+          () => dotenv.loadFromString(
+                envString: '',
+                overrideWith: ['OVERRIDE_KEY=override_value'],
+                isOptional: false,
+              ),
+          throwsA(isA<EmptyEnvFileError>()));
+    });
+  });
 }
diff --git a/test/empty_env_test.dart b/test/empty_env_test.dart
index 01d9e14..68b56ce 100644
--- a/test/empty_env_test.dart
+++ b/test/empty_env_test.dart
@@ -30,7 +30,7 @@ void main() {
       }, throwsA(isA<EmptyEnvFileError>()));
     });
 
-    test('missing .env file with isOptional=true should not throw', () {
+    test('empty string with isOptional=true should not throw', () {
       File emptyFile = File('test/.env.empty');
       expect(() {
         dotenv.loadFromString(
@@ -41,8 +41,7 @@ void main() {
       expect(dotenv.env.isEmpty, isTrue);
     });
 
-    test(
-        'missing .env file with isOptional=false should throw FileNotFoundError',
+    test('empty string with isOptional=false should throw EmptyEnvFileError',
         () {
       expect(() {
         dotenv.loadFromString(envString: '', isOptional: false);