diff --git a/README.md b/README.md
index 01d9549..288351c 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,8 @@
-Provides [source_gen](https://pub.dev/packages/source_gen) `Generator` for generating `copyWith` extensions. For more info on this package check out [my blog article](https://www.alexander-kirsch.com/blog/dart-extensions/) or the [main documentation file](https://pub.dev/packages/copy_with_extension_gen).
+Provides [Dart Build System](https://pub.dev/packages/build) builder for generating `copyWith` extensions for classes annotated with [copy_with_extension](https://pub.dev/packages/copy_with_extension).
+
+For more information on how to use this package, see [copy_with_extension_gen](https://pub.dev/packages/copy_with_extension_gen).
+
+For more information on how this package works, see [my blog article](https://alexander-kirsch.com/blog/dart-extensions).
 
 ## copy_with_extension
 * Package: [copy_with_extension](https://pub.dev/packages/copy_with_extension)
diff --git a/copy_with_extension/CHANGELOG.md b/copy_with_extension/CHANGELOG.md
index 2af98c9..3f4a3bf 100644
--- a/copy_with_extension/CHANGELOG.md
+++ b/copy_with_extension/CHANGELOG.md
@@ -1,8 +1,12 @@
+## 4.0.0
+* **BREAKING** `copyWith` function now correctly supports nullification of nullable fields like so `copyWith(id: null)`.
+* **BREAKING** `CopyWith` annotation for named constructor `namedConstructor` is renamed to `constructor` to be in sync with [json_serializable](https://pub.dev/packages/json_serializable).
+
 ## 3.0.0
 * Updating `analyzer` to `>=2.0.0 <4.0.0`
 * Named constructor support.
 * Better error reporting.
-* Introduction of the new `copyWith` function with nullability support. The default behaviour of this library assumes that this function is used as follows: `myInstance.copyWith.value("newValue")`. The old functionality is still available.
+* Introduction of the new `copyWith` function with nullability support that can be used like so: `myInstance.copyWith.value("newValue")`. The old functionality is still available.
 * **BREAKING** `generateCopyWithNull` is renamed to `copyWithNull`.
 
 ## 2.0.3 Dependency update
diff --git a/copy_with_extension/example/example.dart b/copy_with_extension/example/example.dart
index 8f7f177..1a5989d 100644
--- a/copy_with_extension/example/example.dart
+++ b/copy_with_extension/example/example.dart
@@ -26,7 +26,7 @@ class SimpleObjectImmutableField {
 }
 
 /// Allows the use of a private constructor.
-@CopyWith(namedConstructor: "_")
+@CopyWith(constructor: "_")
 class SimpleObjectPrivateConstructor {
   @CopyWithField(immutable: true)
   final String? id;
diff --git a/copy_with_extension/lib/copy_with_extension.dart b/copy_with_extension/lib/copy_with_extension.dart
index e4d47a7..a414269 100644
--- a/copy_with_extension/lib/copy_with_extension.dart
+++ b/copy_with_extension/lib/copy_with_extension.dart
@@ -1,5 +1,4 @@
-/// Provides annotation class to use with
-/// [copy_with_extension_gen](https://pub.dev/packages/copy_with_extension_gen).
+/// Provides `CopyWith` annotation class used by [copy_with_extension_gen](https://pub.dev/packages/copy_with_extension_gen).
 library copy_with_extension;
 
 /// Annotation used to indicate that the `copyWith` extension should be generated.
@@ -7,23 +6,28 @@ class CopyWith {
   const CopyWith({
     this.copyWithNull = false,
     this.skipFields = false,
-    this.namedConstructor,
+    this.constructor,
   });
 
-  /// Set `copyWithNull` to `true` if you want to use `copyWithNull` function that allows you to nullify the fields. E.g. `myInstance.copyWithNull(id: true, name: true)`. Otherwise it will be still generated for internal use but marked as private.
+  /// Set `copyWithNull` to `true` if you want to use `copyWithNull` function that allows you to nullify the fields. E.g. `myInstance.copyWithNull(id: true, name: true)`.
   final bool copyWithNull;
 
-  /// Prevent the library from generating copyWith function for individual filelds. If you want to use only copyWith(...) function.
+  /// Prevent the library from generating `copyWith` functions for individual filelds e.g. `instance.copyWith.id("123")`. If you want to use only copyWith(...) function.
   final bool skipFields;
 
-  /// Set `namedConstructor` if you want to use a named constructor instead. The generated fields will be derived from this constructor.
-  final String? namedConstructor;
+  /// Set `constructor` if you want to use a named constructor. The generated fields will be derived from this constructor.
+  final String? constructor;
 }
 
 /// Additional field related options for the `CopyWith`.
 class CopyWithField {
   const CopyWithField({this.immutable = false});
 
-  /// Indicates that the field should be hidden in the generated `copyWith` method. By setting this flag to `true` the field will always be copied as it is e.g. `userID` field.
+  /// Indicates that the field should be hidden in the generated `copyWith` method. By setting this flag to `true` the field will always be copied as it and excluded from `copyWith` interface.
   final bool immutable;
 }
+
+/// This placeholder object is a default value for nullable fields to handle cases when the user wants to nullify the value.
+class $CopyWithPlaceholder {
+  const $CopyWithPlaceholder();
+}
diff --git a/copy_with_extension/pubspec.yaml b/copy_with_extension/pubspec.yaml
index 4f30eba..bee54ba 100644
--- a/copy_with_extension/pubspec.yaml
+++ b/copy_with_extension/pubspec.yaml
@@ -1,5 +1,5 @@
 name: copy_with_extension
-version: 3.0.0
+version: 4.0.0
 description: Annotation for generating `copyWith` extensions code using `copy_with_extension_gen`.
 homepage: https://github.com/numen31337/copy_with_extension/tree/master/copy_with_extension
 repository: https://github.com/numen31337/copy_with_extension
@@ -9,4 +9,4 @@ environment:
   sdk: ">=2.12.0 <3.0.0"
 
 dev_dependencies:
-  flutter_lints: ^1.0.0
\ No newline at end of file
+  flutter_lints: ^1.0.0
diff --git a/copy_with_extension_gen/CHANGELOG.md b/copy_with_extension_gen/CHANGELOG.md
index 2af98c9..3f4a3bf 100644
--- a/copy_with_extension_gen/CHANGELOG.md
+++ b/copy_with_extension_gen/CHANGELOG.md
@@ -1,8 +1,12 @@
+## 4.0.0
+* **BREAKING** `copyWith` function now correctly supports nullification of nullable fields like so `copyWith(id: null)`.
+* **BREAKING** `CopyWith` annotation for named constructor `namedConstructor` is renamed to `constructor` to be in sync with [json_serializable](https://pub.dev/packages/json_serializable).
+
 ## 3.0.0
 * Updating `analyzer` to `>=2.0.0 <4.0.0`
 * Named constructor support.
 * Better error reporting.
-* Introduction of the new `copyWith` function with nullability support. The default behaviour of this library assumes that this function is used as follows: `myInstance.copyWith.value("newValue")`. The old functionality is still available.
+* Introduction of the new `copyWith` function with nullability support that can be used like so: `myInstance.copyWith.value("newValue")`. The old functionality is still available.
 * **BREAKING** `generateCopyWithNull` is renamed to `copyWithNull`.
 
 ## 2.0.3 Dependency update
diff --git a/copy_with_extension_gen/README.md b/copy_with_extension_gen/README.md
index 041b960..7139fb2 100644
--- a/copy_with_extension_gen/README.md
+++ b/copy_with_extension_gen/README.md
@@ -5,9 +5,9 @@ Provides [Dart Build System](https://pub.dev/packages/build) builder for generat
 This library allows you to copy instances of immutable classes modifying specific fields like so:
 
 ```dart
-myInstance.copyWith.fieldName("test") // Preferred way with nullability support.
+myInstance.copyWith.fieldName("test") // Change a single field.
 
-myInstance.copyWith(fieldName: "test", anotherField: "test") // Change multiple fields at once without nullability support.
+myInstance.copyWith(fieldName: "test", anotherField: "test", nullableField: null) // Change multiple fields at once.
 
 myInstance.copyWithNull(fieldName: true, anotherField: true) // Nullify multiple fields at once.
 ```
@@ -16,8 +16,8 @@ myInstance.copyWithNull(fieldName: true, anotherField: true) // Nullify multiple
 ## Usage
 
 #### In your `pubspec.yaml` file:
-- Add to `dependencies` section `copy_with_extension: ^3.0.0`
-- Add to `dev_dependencies` section `copy_with_extension_gen: ^3.0.0`
+- Add to `dependencies` section `copy_with_extension: ^4.0.0`
+- Add to `dev_dependencies` section `copy_with_extension_gen: ^4.0.0`
 - Add to `dev_dependencies` section `build_runner: ^2.1.7`
 - Set `environment` to at least Dart `2.12.0` version like so: `">=2.12.0 <3.0.0"`
 
@@ -33,12 +33,12 @@ environment:
 
 dependencies:
   ...
-  copy_with_extension: ^3.0.0
+  copy_with_extension: ^4.0.0
   
 dev_dependencies:
   ...
   build_runner: ^2.1.7
-  copy_with_extension_gen: ^3.0.0
+  copy_with_extension_gen: ^4.0.0
 ```
 
 #### Annotate your class with `CopyWith` annotation:
@@ -69,18 +69,19 @@ flutter pub run build_runner build
 
 ```dart
 const result = BasicClass(id: "id")
-final copied = result.copyWith.text("test") // Results in BasicClass(id: "id", text: "test");
+final copiedOne = result.copyWith.text("test") // Results in BasicClass(id: "id", text: "test");
+final copiedTwo = result.copyWith(id: "foo", text: null) // Results in BasicClass(id: "foo", text: null);
 ```
 
 ## Additional features
 
 #### Change several fields at once with copyWith()
 
-You can modify multiple fields at once using `copyWith` as a function like so: `myInstance.copyWith(fieldName: "test", anotherField: "test")`. Be aware that this kind of usage does not support nullification and all passed `null` values will be ignored.
+You can modify multiple fields at once using `copyWith` as a function like so: `myInstance.copyWith(fieldName: "test", anotherField: "test")`. Passing the `null` value to `non-nullable` fields will be ignored.
 
 #### Nullifying instance fields:
 
-The `copyWith` method ignores any `null` values that are passed to it. In order to nullify the class fields, an additional `copyWithNull` function can be generated. To achieve this, simply pass an additional parameter to your class annotation `@CopyWith(generateCopyWithNull: true)`.
+In order to nullify the class fields, an additional `copyWithNull` function can be generated. To make use of it, pass an additional parameter to your class annotation `@CopyWith(generateCopyWithNull: true)`.
 
 #### Immutable fields
 
@@ -91,4 +92,8 @@ If you want to prevent a particular field from modifying with `copyWith` method
 final int myImmutableField;
 ```
 
-By adding this annotation you forcing your generated `copyWith` to always copy this field as it is, without allowing its modification.
+By adding this annotation you forcing your generated `copyWith` to always copy this field as it is, without exposing it in the function interface.
+
+## How this library is better than `freezed`?
+
+It isn't. This library is a non-intrusive alternative for those who only need the `copyWith` functionality and do not want to maintain the codebase in the way implied by the framework. This library only requires from your side the annotation of your class with `CopyWith()` and an indication of the `.part` file, everything else is up to you. [`freezed`](https://pub.dev/packages/freezed), on the other hand, offers many more code generation features but requires your models to be written in a framework-specific manner.
diff --git a/copy_with_extension_gen/analysis_options.yaml b/copy_with_extension_gen/analysis_options.yaml
index 0ffcdb2..35d4188 100644
--- a/copy_with_extension_gen/analysis_options.yaml
+++ b/copy_with_extension_gen/analysis_options.yaml
@@ -3,4 +3,8 @@ include: package:flutter_lints/flutter.yaml
 analyzer:
   strong-mode:
     implicit-casts: false
-    implicit-dynamic: false
\ No newline at end of file
+    implicit-dynamic: false
+
+linter:
+  rules:
+    cast_nullable_to_non_nullable: true
\ No newline at end of file
diff --git a/copy_with_extension_gen/example/example.dart b/copy_with_extension_gen/example/example.dart
index 8f7f177..1a5989d 100644
--- a/copy_with_extension_gen/example/example.dart
+++ b/copy_with_extension_gen/example/example.dart
@@ -26,7 +26,7 @@ class SimpleObjectImmutableField {
 }
 
 /// Allows the use of a private constructor.
-@CopyWith(namedConstructor: "_")
+@CopyWith(constructor: "_")
 class SimpleObjectPrivateConstructor {
   @CopyWithField(immutable: true)
   final String? id;
diff --git a/copy_with_extension_gen/lib/src/copy_with_generator.dart b/copy_with_extension_gen/lib/src/copy_with_generator.dart
index caf9ca9..bff4a05 100644
--- a/copy_with_extension_gen/lib/src/copy_with_generator.dart
+++ b/copy_with_extension_gen/lib/src/copy_with_generator.dart
@@ -25,27 +25,26 @@ class CopyWithGenerator extends GeneratorForAnnotation<CopyWith> {
     final classAnnotation = readClassAnnotation(annotation);
 
     final sortedFields =
-        sortedConstructorFields(classElement, classAnnotation.namedConstructor);
+        sortedConstructorFields(classElement, classAnnotation.constructor);
     final typeParametersAnnotation = typeParametersString(classElement, false);
     final typeParametersNames = typeParametersString(classElement, true);
     final typeAnnotation = classElement.name + typeParametersNames;
 
     return '''
     ${_copyWithProxyPart(
-      classAnnotation.namedConstructor,
+      classAnnotation.constructor,
       classElement.name,
       typeParametersAnnotation,
       typeParametersNames,
       sortedFields,
-      !classAnnotation.copyWithNull,
       classAnnotation.skipFields,
     )}
     
-    extension ${classElement.name}CopyWith$typeParametersAnnotation on ${classElement.name}$typeParametersNames {
-      /// CopyWith feature provided by `copy_with_extension_gen` library. Returns a callable class and can be used as follows: `instanceOf$classElement.name.copyWith(...)`. Be aware that this kind of usage does not support nullification and all passed `null` values will be ignored.${classAnnotation.skipFields ? "" : " Prefer to copy the instance with a specific field change that handles nullification of fields correctly, e.g. like this:`instanceOf$classElement.name.copyWith.fieldName(...)`"}
-      ${"_${classElement.name}CWProxy$typeParametersNames get copyWith => _${classElement.name}CWProxy$typeParametersNames(this);"}
+    extension \$${classElement.name}CopyWith$typeParametersAnnotation on ${classElement.name}$typeParametersNames {
+      /// Returns a callable class that can be used as follows: `instanceOf$classElement.name.copyWith(...)`${classAnnotation.skipFields ? "" : " or like so:`instanceOf$classElement.name.copyWith.fieldName(...)`"}.
+      ${"_\$${classElement.name}CWProxy$typeParametersNames get copyWith => _\$${classElement.name}CWProxyImpl$typeParametersNames(this);"}
 
-      ${_copyWithNullPart(typeAnnotation, sortedFields, classAnnotation.namedConstructor, !classAnnotation.copyWithNull, classAnnotation.skipFields)}
+      ${classAnnotation.copyWithNull ? _copyWithNullPart(typeAnnotation, sortedFields, classAnnotation.constructor, classAnnotation.skipFields) : ""}
     }
     ''';
   }
@@ -54,41 +53,49 @@ class CopyWithGenerator extends GeneratorForAnnotation<CopyWith> {
   String _copyWithValuesPart(
     String typeAnnotation,
     List<FieldInfo> sortedFields,
-    String? namedConstructor,
+    String? constructor,
     bool skipFields,
+    bool isAbstract,
   ) {
     final constructorInput = sortedFields.fold<String>(
       '',
       (r, v) {
-        if (v.immutable) {
-          return r;
-        } else {
+        if (v.immutable) return r; // Skip the field
+
+        if (isAbstract) {
           final type = v.type.endsWith('?') ? v.type : '${v.type}?';
           return '$r $type ${v.name},';
+        } else {
+          return '$r Object? ${v.name} = const \$CopyWithPlaceholder(),';
         }
       },
     );
     final paramsInput = sortedFields.fold<String>(
       '',
       (r, v) {
-        if (v.immutable) {
-          return '$r ${v.name}: _value.${v.name},';
-        } else {
-          return '$r ${v.name}: ${v.name} ?? _value.${v.name},';
-        }
+        if (v.immutable) return '$r ${v.name}: _value.${v.name},';
+
+        return '''
+        $r ${v.name}:
+        ${v.name} == const \$CopyWithPlaceholder() 
+        ? _value.${v.name}
+        // ignore: cast_nullable_to_non_nullable
+        : ${v.name} as ${v.type},''';
       },
     );
 
+    final constructorBody = isAbstract
+        ? ""
+        : "{ return ${constructorFor(typeAnnotation, constructor)}($paramsInput); }";
+
     return '''
-        /// This function does not support nullification of optional types, all `null` values passed to this function will be ignored. For nullification, use `$typeAnnotation(...).copyWithNull(...)` to set certain fields to `null`.${skipFields ? "" : " Prefer `$typeAnnotation(...).copyWith.fieldName(...)` to override fields one at a time with nullification support."}
+        /// This function **does support** nullification of nullable fields. All `null` values passed to `non-nullable` fields will be ignored.${skipFields ? "" : " You can also use `$typeAnnotation(...).copyWith.fieldName(...)` to override fields one at a time with nullification support."}
         /// 
         /// Usage
         /// ```dart
         /// $typeAnnotation(...).copyWith(id: 12, name: "My name")
         /// ````
-        $typeAnnotation call({$constructorInput}) {
-          return ${constructorFor(typeAnnotation, namedConstructor)}($paramsInput);
-        }
+        $typeAnnotation call({$constructorInput}) $constructorBody
     ''';
   }
 
@@ -96,8 +103,7 @@ class CopyWithGenerator extends GeneratorForAnnotation<CopyWith> {
   String _copyWithNullPart(
     String typeAnnotation,
     List<FieldInfo> sortedFields,
-    String? namedConstructor,
-    bool private,
+    String? constructor,
     bool skipFields,
   ) {
     /// Return if there is no nullable fields
@@ -126,60 +132,60 @@ class CopyWithGenerator extends GeneratorForAnnotation<CopyWith> {
       },
     );
 
-    final description = private
-        ? ""
-        : '''
-        /// Copies the object with the specific fields set to `null`. If you pass `false` as a parameter, nothing will be done and it will be ignored. Don't do it.${skipFields ? "" : " Prefer `$typeAnnotation(...).copyWith.fieldName(...)` to override fields one at a time with nullification support."}
-        ///
-        /// Usage
-        /// ```dart
-        /// $typeAnnotation(...).copyWithNull(firstField: true, secondField: true)
-        /// ````''';
+    final description = '''
+    /// Copies the object with the specific fields set to `null`. If you pass `false` as a parameter, nothing will be done and it will be ignored. Don't do it. Prefer `copyWith(field: null)`${skipFields ? "" : " or `$typeAnnotation(...).copyWith.fieldName(...)` to override fields one at a time with nullification support"}.
+    ///
+    /// Usage
+    /// ```dart
+    /// $typeAnnotation(...).copyWithNull(firstField: true, secondField: true)
+    /// ````''';
 
     return '''
       $description
-      $typeAnnotation ${private ? "_" : ""}copyWithNull({$nullConstructorInput}) {
-        return ${constructorFor(typeAnnotation, namedConstructor)}($nullParamsInput);
+      $typeAnnotation copyWithNull({$nullConstructorInput}) {
+        return ${constructorFor(typeAnnotation, constructor)}($nullParamsInput);
       }
-    ''';
+     ''';
   }
 
   /// Generates a `CopyWithProxy` class.
   String _copyWithProxyPart(
-    String? namedConstructor,
+    String? constructor,
     String type,
     String typeParameters,
     String typeParameterNames,
     List<FieldInfo> sortedFields,
-    bool privateCopyWithNull,
     bool skipFields,
   ) {
     final typeAnnotation = type + typeParameterNames;
     final filteredFields = sortedFields.where((e) => !e.immutable);
-    final nonNullableFields = filteredFields.where((e) => !e.nullable);
-    final nullableFields =
-        filteredFields.where((e) => !nonNullableFields.contains(e));
 
-    final nonNullableFunctions =
-        skipFields ? "" : nonNullableFields.map((e) => '''
+    final nonNullableFunctions = skipFields ? "" : filteredFields.map((e) => '''
+    @override
     $type$typeParameterNames ${e.name}(${e.type} ${e.name}) => this(${e.name}: ${e.name});
     ''').join("\n");
-    final nullableFunctions = skipFields ? "" : nullableFields.map((e) => '''
-    $type$typeParameterNames ${e.name}(${e.type} ${e.name}) => ${e.name} == null ? _value.${privateCopyWithNull ? "_" : ""}copyWithNull(${e.name}: true) : this(${e.name}: ${e.name});
+    final nonNullableFunctionsInterface =
+        skipFields ? "" : filteredFields.map((e) => '''
+    $type$typeParameterNames ${e.name}(${e.type} ${e.name});
     ''').join("\n");
 
     return '''
-      /// Proxy class for `CopyWith` functionality. This is a callable class and can be used as follows: `instanceOf$type.copyWith(...)`. Be aware that this kind of usage does not support nullification and all passed `null` values will be ignored.${skipFields ? "" : " Prefer to copy the instance with a specific field change that handles nullification of fields correctly, e.g. like this:`instanceOf$type.copyWith.fieldName(...)`"}
-      class _${type}CWProxy$typeParameters {
-        final $type$typeParameterNames _value;
+      abstract class _\$${type}CWProxy$typeParameters {
+        $nonNullableFunctionsInterface
 
-        const _${type}CWProxy(this._value);
+        ${_copyWithValuesPart(typeAnnotation, sortedFields, constructor, skipFields, true)};
+      }
 
-        ${_copyWithValuesPart(typeAnnotation, sortedFields, namedConstructor, skipFields)}
+      /// Proxy class for `copyWith` functionality. This is a callable class and can be used as follows: `instanceOf$type.copyWith(...)`.${skipFields ? "" : " Additionally contains functions for specific fields e.g. `instanceOf$type.copyWith.fieldName(...)`"}
+      class _\$${type}CWProxyImpl$typeParameters implements _\$${type}CWProxy$typeParameterNames {
+        final $type$typeParameterNames _value;
 
-        $nullableFunctions
+        const _\$${type}CWProxyImpl(this._value);
 
         $nonNullableFunctions
+
+        @override
+        ${_copyWithValuesPart(typeAnnotation, sortedFields, constructor, skipFields, false)}
       }
     ''';
   }
diff --git a/copy_with_extension_gen/lib/src/field_info.dart b/copy_with_extension_gen/lib/src/field_info.dart
index cf2fff0..a3ab429 100644
--- a/copy_with_extension_gen/lib/src/field_info.dart
+++ b/copy_with_extension_gen/lib/src/field_info.dart
@@ -40,8 +40,10 @@ class FieldInfo {
     }
 
     final reader = ConstantReader(annotation);
-    final immutable = reader.read('immutable').literalValue as bool;
+    final immutable = reader.read('immutable').literalValue as bool?;
 
-    return CopyWithField(immutable: immutable);
+    return CopyWithField(
+      immutable: immutable ?? const CopyWithField().immutable,
+    );
   }
 }
diff --git a/copy_with_extension_gen/lib/src/helpers.dart b/copy_with_extension_gen/lib/src/helpers.dart
index c03d0b6..c8c4852 100644
--- a/copy_with_extension_gen/lib/src/helpers.dart
+++ b/copy_with_extension_gen/lib/src/helpers.dart
@@ -9,16 +9,16 @@ import 'package:source_gen/source_gen.dart'
 /// The resulting array is sorted by the field name. `Throws` on error.
 List<FieldInfo> sortedConstructorFields(
   ClassElement element,
-  String? constructorName,
+  String? constructor,
 ) {
-  final constructor = constructorName != null
-      ? element.getNamedConstructor(constructorName)
+  final targetConstructor = constructor != null
+      ? element.getNamedConstructor(constructor)
       : element.unnamedConstructor;
 
-  if (constructor is! ConstructorElement) {
-    if (constructorName != null) {
+  if (targetConstructor is! ConstructorElement) {
+    if (constructor != null) {
       throw InvalidGenerationSourceError(
-        'Named Constructor "$constructorName" constructor is missing.',
+        'Named Constructor "$constructor" constructor is missing.',
         element: element,
       );
     } else {
@@ -29,7 +29,7 @@ List<FieldInfo> sortedConstructorFields(
     }
   }
 
-  final parameters = constructor.parameters;
+  final parameters = targetConstructor.parameters;
   if (parameters.isEmpty) {
     throw InvalidGenerationSourceError(
       'Unnamed constructor for ${element.name} has no parameters or missing.',
@@ -39,9 +39,9 @@ List<FieldInfo> sortedConstructorFields(
 
   for (final parameter in parameters) {
     if (!parameter.isNamed) {
-      final constructorName = constructor.name.isEmpty
+      final constructorName = targetConstructor.name.isEmpty
           ? 'Unnamed constructor'
-          : 'Constructor "${constructor.name}"';
+          : 'Constructor "${targetConstructor.name}"';
       throw InvalidGenerationSourceError(
         '$constructorName for "${element.name}" contains unnamed parameter "${parameter.name}". Constructors annotated with "CopyWith" can contain only named parameters.',
         element: element,
@@ -59,11 +59,11 @@ List<FieldInfo> sortedConstructorFields(
 CopyWith readClassAnnotation(ConstantReader reader) {
   final generateCopyWithNull = reader.read('copyWithNull').boolValue;
   final skipFields = reader.read('skipFields').boolValue;
-  final useNamedConstructor = reader.peek('namedConstructor')?.stringValue;
+  final constructor = reader.peek('constructor')?.stringValue;
 
   return CopyWith(
     copyWithNull: generateCopyWithNull,
-    namedConstructor: useNamedConstructor,
+    constructor: constructor,
     skipFields: skipFields,
   );
 }
diff --git a/copy_with_extension_gen/pubspec.yaml b/copy_with_extension_gen/pubspec.yaml
index 9ffc028..08ad1cd 100644
--- a/copy_with_extension_gen/pubspec.yaml
+++ b/copy_with_extension_gen/pubspec.yaml
@@ -1,5 +1,5 @@
 name: copy_with_extension_gen
-version: 3.0.0
+version: 4.0.0
 description: Automatically generating `copyWith` extensions code for classes with `@CopyWith()` annotation.
 repository: https://github.com/numen31337/copy_with_extension
 homepage: https://github.com/numen31337/copy_with_extension/tree/master/copy_with_extension_gen
@@ -9,13 +9,13 @@ environment:
   sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
-  analyzer: '>=2.0.0 <4.0.0'
+  analyzer: ">=2.0.0 <4.0.0"
   build: ^2.0.0
   source_gen: ^1.0.0
-  copy_with_extension: ^3.0.0
+  copy_with_extension: ^4.0.0
 
 dev_dependencies:
   flutter_lints: ^1.0.0
   build_runner: ">=1.11.5 <3.0.0"
   test: ^1.20.1
-  source_gen_test: ^1.0.1
\ No newline at end of file
+  source_gen_test: ^1.0.1
diff --git a/copy_with_extension_gen/test/gen_basic_functionality_test.dart b/copy_with_extension_gen/test/gen_basic_functionality_test.dart
index 83db0f0..6964ff8 100644
--- a/copy_with_extension_gen/test/gen_basic_functionality_test.dart
+++ b/copy_with_extension_gen/test/gen_basic_functionality_test.dart
@@ -67,6 +67,11 @@ void main() {
       const CopyWithValuesOptional(id: "test").copyWith.id(null).id,
       null,
     );
+
+    expect(
+      const CopyWithValuesOptional(id: "test").copyWith(id: null).id,
+      null,
+    );
   });
 
   test('CopyWithProxy', () {
diff --git a/copy_with_extension_gen/test/gen_inheritance_test.dart b/copy_with_extension_gen/test/gen_inheritance_test.dart
index 2df61a2..84e8ff4 100644
--- a/copy_with_extension_gen/test/gen_inheritance_test.dart
+++ b/copy_with_extension_gen/test/gen_inheritance_test.dart
@@ -93,18 +93,13 @@ void main() {
       id: "testid",
       date: date,
       listWithTypedType: const [],
-    )._copyWithNull().copyWith();
+    ).copyWith();
 
     expect(
       result.copyWith().runtimeType,
       ComplexSubClass<int, String>(id: "", date: date).runtimeType,
     );
 
-    expect(
-      result._copyWithNull().runtimeType,
-      ComplexSubClass<int, String>(id: "", date: date).runtimeType,
-    );
-
     expect(
       result.copyWith.id("").runtimeType,
       ComplexSubClass<int, String>(id: "", date: date).runtimeType,
@@ -112,7 +107,7 @@ void main() {
 
     expect(
       result.copyWith.runtimeType,
-      _ComplexSubClassCWProxy<int, String>(
+      _$ComplexSubClassCWProxyImpl<int, String>(
         ComplexSubClass<int, String>(id: "", date: date),
       ).runtimeType,
     );
diff --git a/copy_with_extension_gen/test/gen_named_constructor_test.dart b/copy_with_extension_gen/test/gen_named_constructor_test.dart
index ba5b41d..a332051 100644
--- a/copy_with_extension_gen/test/gen_named_constructor_test.dart
+++ b/copy_with_extension_gen/test/gen_named_constructor_test.dart
@@ -3,7 +3,7 @@ import 'package:test/test.dart' show test, expect;
 
 part 'gen_named_constructor_test.g.dart';
 
-@CopyWith(namedConstructor: "_")
+@CopyWith(constructor: "_")
 class CopyWithNamedConstructor {
   final String? id;
 
@@ -12,7 +12,7 @@ class CopyWithNamedConstructor {
   });
 }
 
-@CopyWith(namedConstructor: "first")
+@CopyWith(constructor: "first")
 class CopyWithTwoThreeConstructors {
   final String? id;
   final String field;
@@ -32,7 +32,7 @@ class CopyWithTwoThreeConstructors {
   });
 }
 
-@CopyWith(namedConstructor: "_")
+@CopyWith(constructor: "_")
 class DefaultValuesConstructor {
   final String? id = "test";
   final String? field;
diff --git a/copy_with_extension_gen/test/generated_code_test_cases/test_case_basic_usage.dart b/copy_with_extension_gen/test/generated_code_test_cases/test_case_basic_usage.dart
index f5ac8a8..2a762ef 100644
--- a/copy_with_extension_gen/test/generated_code_test_cases/test_case_basic_usage.dart
+++ b/copy_with_extension_gen/test/generated_code_test_cases/test_case_basic_usage.dart
@@ -1,13 +1,12 @@
 part of 'source_gen_entrypoint.dart';
 
 @ShouldGenerate(r'''
-/// Proxy class for `CopyWith` functionality. This is a callable class and can be used as follows: `instanceOfBasicClass.copyWith(...)`. Be aware that this kind of usage does not support nullification and all passed `null` values will be ignored. Prefer to copy the instance with a specific field change that handles nullification of fields correctly, e.g. like this:`instanceOfBasicClass.copyWith.fieldName(...)`
-class _BasicClassCWProxy<T extends Iterable<int>> {
-  final BasicClass<T> _value;
+abstract class _$BasicClassCWProxy<T extends Iterable<int>> {
+  BasicClass<T> id(String id);
 
-  const _BasicClassCWProxy(this._value);
+  BasicClass<T> optional(T? optional);
 
-  /// This function does not support nullification of optional types, all `null` values passed to this function will be ignored. For nullification, use `BasicClass<T>(...).copyWithNull(...)` to set certain fields to `null`. Prefer `BasicClass<T>(...).copyWith.fieldName(...)` to override fields one at a time with nullification support.
+  /// This function **does support** nullification of nullable fields. All `null` values passed to `non-nullable` fields will be ignored. You can also use `BasicClass<T>(...).copyWith.fieldName(...)` to override fields one at a time with nullification support.
   ///
   /// Usage
   /// ```dart
@@ -16,37 +15,53 @@ class _BasicClassCWProxy<T extends Iterable<int>> {
   BasicClass<T> call({
     String? id,
     T? optional,
-  }) {
-    return BasicClass<T>(
-      id: id ?? _value.id,
-      immutable: _value.immutable,
-      nullableImmutable: _value.nullableImmutable,
-      optional: optional ?? _value.optional,
-    );
-  }
+  });
+}
 
-  BasicClass<T> optional(T? optional) => optional == null
-      ? _value._copyWithNull(optional: true)
-      : this(optional: optional);
+/// Proxy class for `copyWith` functionality. This is a callable class and can be used as follows: `instanceOfBasicClass.copyWith(...)`. Additionally contains functions for specific fields e.g. `instanceOfBasicClass.copyWith.fieldName(...)`
+class _$BasicClassCWProxyImpl<T extends Iterable<int>>
+    implements _$BasicClassCWProxy<T> {
+  final BasicClass<T> _value;
+
+  const _$BasicClassCWProxyImpl(this._value);
 
+  @override
   BasicClass<T> id(String id) => this(id: id);
-}
 
-extension BasicClassCopyWith<T extends Iterable<int>> on BasicClass<T> {
-  /// CopyWith feature provided by `copy_with_extension_gen` library. Returns a callable class and can be used as follows: `instanceOfclass BasicClass<T extends Iterable<int>>.name.copyWith(...)`. Be aware that this kind of usage does not support nullification and all passed `null` values will be ignored. Prefer to copy the instance with a specific field change that handles nullification of fields correctly, e.g. like this:`instanceOfclass BasicClass<T extends Iterable<int>>.name.copyWith.fieldName(...)`
-  _BasicClassCWProxy<T> get copyWith => _BasicClassCWProxy<T>(this);
+  @override
+  BasicClass<T> optional(T? optional) => this(optional: optional);
 
-  BasicClass<T> _copyWithNull({
-    bool optional = false,
+  @override
+
+  /// This function **does support** nullification of nullable fields. All `null` values passed to `non-nullable` fields will be ignored. You can also use `BasicClass<T>(...).copyWith.fieldName(...)` to override fields one at a time with nullification support.
+  ///
+  /// Usage
+  /// ```dart
+  /// BasicClass<T>(...).copyWith(id: 12, name: "My name")
+  /// ````
+  BasicClass<T> call({
+    Object? id = const $CopyWithPlaceholder(),
+    Object? optional = const $CopyWithPlaceholder(),
   }) {
     return BasicClass<T>(
-      id: id,
-      immutable: immutable,
-      nullableImmutable: nullableImmutable,
-      optional: optional == true ? null : this.optional,
+      id: id == const $CopyWithPlaceholder()
+          ? _value.id
+          // ignore: cast_nullable_to_non_nullable
+          : id as String,
+      immutable: _value.immutable,
+      nullableImmutable: _value.nullableImmutable,
+      optional: optional == const $CopyWithPlaceholder()
+          ? _value.optional
+          // ignore: cast_nullable_to_non_nullable
+          : optional as T?,
     );
   }
 }
+
+extension $BasicClassCopyWith<T extends Iterable<int>> on BasicClass<T> {
+  /// Returns a callable class that can be used as follows: `instanceOfclass BasicClass<T extends Iterable<int>>.name.copyWith(...)` or like so:`instanceOfclass BasicClass<T extends Iterable<int>>.name.copyWith.fieldName(...)`.
+  _$BasicClassCWProxy<T> get copyWith => _$BasicClassCWProxyImpl<T>(this);
+}
 ''')
 @CopyWith()
 class BasicClass<T extends Iterable<int>> {
diff --git a/copy_with_extension_gen/test/generated_code_test_cases/test_case_copy_with_null.dart b/copy_with_extension_gen/test/generated_code_test_cases/test_case_copy_with_null.dart
index 515b088..e9bd8c0 100644
--- a/copy_with_extension_gen/test/generated_code_test_cases/test_case_copy_with_null.dart
+++ b/copy_with_extension_gen/test/generated_code_test_cases/test_case_copy_with_null.dart
@@ -1,34 +1,52 @@
 part of 'source_gen_entrypoint.dart';
 
 @ShouldGenerate(r'''
-/// Proxy class for `CopyWith` functionality. This is a callable class and can be used as follows: `instanceOfWithNullableWithoutFields.copyWith(...)`. Be aware that this kind of usage does not support nullification and all passed `null` values will be ignored.
-class _WithNullableWithoutFieldsCWProxy<T extends Iterable<int>> {
+abstract class _$WithNullableWithoutFieldsCWProxy<T extends Iterable<int>> {
+  /// This function **does support** nullification of nullable fields. All `null` values passed to `non-nullable` fields will be ignored.
+  ///
+  /// Usage
+  /// ```dart
+  /// WithNullableWithoutFields<T>(...).copyWith(id: 12, name: "My name")
+  /// ````
+  WithNullableWithoutFields<T> call({
+    T? nullable,
+  });
+}
+
+/// Proxy class for `copyWith` functionality. This is a callable class and can be used as follows: `instanceOfWithNullableWithoutFields.copyWith(...)`.
+class _$WithNullableWithoutFieldsCWProxyImpl<T extends Iterable<int>>
+    implements _$WithNullableWithoutFieldsCWProxy<T> {
   final WithNullableWithoutFields<T> _value;
 
-  const _WithNullableWithoutFieldsCWProxy(this._value);
+  const _$WithNullableWithoutFieldsCWProxyImpl(this._value);
 
-  /// This function does not support nullification of optional types, all `null` values passed to this function will be ignored. For nullification, use `WithNullableWithoutFields<T>(...).copyWithNull(...)` to set certain fields to `null`.
+  @override
+
+  /// This function **does support** nullification of nullable fields. All `null` values passed to `non-nullable` fields will be ignored.
   ///
   /// Usage
   /// ```dart
   /// WithNullableWithoutFields<T>(...).copyWith(id: 12, name: "My name")
   /// ````
   WithNullableWithoutFields<T> call({
-    T? nullable,
+    Object? nullable = const $CopyWithPlaceholder(),
   }) {
     return WithNullableWithoutFields<T>(
-      nullable: nullable ?? _value.nullable,
+      nullable: nullable == const $CopyWithPlaceholder()
+          ? _value.nullable
+          // ignore: cast_nullable_to_non_nullable
+          : nullable as T?,
     );
   }
 }
 
-extension WithNullableWithoutFieldsCopyWith<T extends Iterable<int>>
+extension $WithNullableWithoutFieldsCopyWith<T extends Iterable<int>>
     on WithNullableWithoutFields<T> {
-  /// CopyWith feature provided by `copy_with_extension_gen` library. Returns a callable class and can be used as follows: `instanceOfclass WithNullableWithoutFields<T extends Iterable<int>>.name.copyWith(...)`. Be aware that this kind of usage does not support nullification and all passed `null` values will be ignored.
-  _WithNullableWithoutFieldsCWProxy<T> get copyWith =>
-      _WithNullableWithoutFieldsCWProxy<T>(this);
+  /// Returns a callable class that can be used as follows: `instanceOfclass WithNullableWithoutFields<T extends Iterable<int>>.name.copyWith(...)`.
+  _$WithNullableWithoutFieldsCWProxy<T> get copyWith =>
+      _$WithNullableWithoutFieldsCWProxyImpl<T>(this);
 
-  /// Copies the object with the specific fields set to `null`. If you pass `false` as a parameter, nothing will be done and it will be ignored. Don't do it.
+  /// Copies the object with the specific fields set to `null`. If you pass `false` as a parameter, nothing will be done and it will be ignored. Don't do it. Prefer `copyWith(field: null)`.
   ///
   /// Usage
   /// ```dart
diff --git a/copy_with_extension_gen/test/generated_code_test_cases/test_cases_exceptions.dart b/copy_with_extension_gen/test/generated_code_test_cases/test_cases_exceptions.dart
index 95134d8..17299f1 100644
--- a/copy_with_extension_gen/test/generated_code_test_cases/test_cases_exceptions.dart
+++ b/copy_with_extension_gen/test/generated_code_test_cases/test_cases_exceptions.dart
@@ -15,7 +15,7 @@ class NoConstructor {
 }
 
 @ShouldThrow('Named Constructor "test" constructor is missing.')
-@CopyWith(namedConstructor: "test")
+@CopyWith(constructor: "test")
 class WrongConstructor {}
 
 @ShouldThrow('Default constructor for "NoDefaultConstructor" is missing.')
@@ -49,7 +49,7 @@ class ConstructorWithAllUnnamedFields {
 @ShouldThrow(
   'Constructor "test" for "NamedConstructorWithSomeUnnamedFields" contains unnamed parameter "value". Constructors annotated with "CopyWith" can contain only named parameters.',
 )
-@CopyWith(namedConstructor: "test")
+@CopyWith(constructor: "test")
 class NamedConstructorWithSomeUnnamedFields {
   int? test;
   int value;