diff --git a/angel_serialize_generator/lib/angel_serialize_generator.dart b/angel_serialize_generator/lib/angel_serialize_generator.dart
index fb22821e..8287cfae 100644
--- a/angel_serialize_generator/lib/angel_serialize_generator.dart
+++ b/angel_serialize_generator/lib/angel_serialize_generator.dart
@@ -9,7 +9,6 @@ import 'package:code_builder/code_builder.dart';
 import 'package:source_gen/source_gen.dart' hide LibraryBuilder;
 import 'build_context.dart';
 import 'context.dart';
-
 part 'model.dart';
 
 /// Converts a [DartType] to a [TypeReference].
@@ -21,81 +20,4 @@ TypeReference convertTypeReference(DartType t) {
       b.types.addAll(t.typeArguments.map(convertTypeReference));
     }
   });
-}
-
-class JsonModelGenerator extends GeneratorForAnnotation<Serializable> {
-  final bool autoSnakeCaseNames;
-  final bool autoIdAndDateFields;
-
-  const JsonModelGenerator(
-      {this.autoSnakeCaseNames: true, this.autoIdAndDateFields: true});
-
-  @override
-  Future<String> generateForAnnotatedElement(
-      Element element, ConstantReader reader, BuildStep buildStep) async {
-    if (element.kind != ElementKind.CLASS)
-      throw 'Only classes can be annotated with a @Serializable() annotation.';
-
-    var ctx = await buildContext(
-        element,
-        serializable,
-        buildStep,
-        await buildStep.resolver,
-        autoSnakeCaseNames != false,
-        autoIdAndDateFields != false);
-
-    var lib = new File((b) {
-      generateClass(ctx, b);
-    });
-
-    var buf = lib.accept(new DartEmitter());
-    return buf.toString();
-  }
-
-  /// Generate an extended model class.
-  void generateClass(BuildContext ctx, FileBuilder file) {
-    file.body.add(new Class((clazz) {
-      clazz
-        ..name = ctx.modelClassNameRecase.pascalCase
-        ..extend = new Reference(ctx.originalClassName);
-
-      for (var field in ctx.fields) {
-        clazz.fields.add(new Field((b) {
-          b
-            ..name = field.name
-            ..modifier = FieldModifier.final$
-            ..type = convertTypeReference(field.type);
-        }));
-      }
-
-      generateConstructor(ctx, clazz, file);
-      generateChangeMethod(ctx, clazz, file);
-    }));
-  }
-
-  /// Generate a constructor with named parameters.
-  void generateConstructor(
-      BuildContext ctx, ClassBuilder clazz, FileBuilder file) {
-    clazz.constructors.add(new Constructor((constructor) {
-      for (var field in ctx.fields) {
-        constructor.optionalParameters.add(new Parameter((b) {
-          b
-            ..name = field.name
-            ..named = true
-            ..toThis = true;
-        }));
-      }
-    }));
-  }
-
-  /// Generate a `change` method.
-  void generateChangeMethod(
-      BuildContext ctx, ClassBuilder clazz, FileBuilder file) {
-    clazz.methods.add(new Method((method) {
-      method
-        ..name = 'change'
-        ..returns = ctx.modelClassType
-      ..requiredParameters.add(new Parameter());
-    }));
-  }
-}
+}
\ No newline at end of file
diff --git a/angel_serialize_generator/lib/build_context.dart b/angel_serialize_generator/lib/build_context.dart
index cce3cd00..5400747d 100644
--- a/angel_serialize_generator/lib/build_context.dart
+++ b/angel_serialize_generator/lib/build_context.dart
@@ -36,7 +36,9 @@ Future<BuildContext> buildContext(
       fieldNames.add(field.name);
       // Skip if annotated with @exclude
       var excludeAnnotation = excludeTypeChecker.firstAnnotationOf(field);
-      if (excludeAnnotation != null) continue;
+
+      ctx.excluded[field.name] = excludeAnnotation != null;
+
       // Check for alias
       Alias alias;
       var aliasAnn = aliasTypeChecker.firstAnnotationOf(field);
diff --git a/angel_serialize_generator/lib/context.dart b/angel_serialize_generator/lib/context.dart
index 9bf66a9a..b5c99268 100644
--- a/angel_serialize_generator/lib/context.dart
+++ b/angel_serialize_generator/lib/context.dart
@@ -11,6 +11,9 @@ class BuildContext {
   /// A map of field names to resolved names from `@Alias()` declarations.
   final Map<String, String> aliases = {};
 
+  /// A map of fields that have been marked as to be excluded from serialization.
+  final Map<String, bool> excluded = {};
+
   /// A map of "synthetic" fields, i.e. `id` and `created_at` injected automatically.
   final Map<String, bool> shimmed = {};
 
diff --git a/angel_serialize_generator/lib/model.dart b/angel_serialize_generator/lib/model.dart
index 97a17289..f0f599c5 100644
--- a/angel_serialize_generator/lib/model.dart
+++ b/angel_serialize_generator/lib/model.dart
@@ -1,2 +1,98 @@
 part of angel_serialize_generator;
 
+class JsonModelGenerator extends GeneratorForAnnotation<Serializable> {
+  final bool autoSnakeCaseNames;
+  final bool autoIdAndDateFields;
+
+  const JsonModelGenerator(
+      {this.autoSnakeCaseNames: true, this.autoIdAndDateFields: true});
+
+  @override
+  Future<String> generateForAnnotatedElement(
+      Element element, ConstantReader reader, BuildStep buildStep) async {
+    if (element.kind != ElementKind.CLASS)
+      throw 'Only classes can be annotated with a @Serializable() annotation.';
+
+    var ctx = await buildContext(
+        element,
+        serializable,
+        buildStep,
+        await buildStep.resolver,
+        autoSnakeCaseNames != false,
+        autoIdAndDateFields != false);
+
+    var lib = new File((b) {
+      generateClass(ctx, b);
+    });
+
+    var buf = lib.accept(new DartEmitter());
+    return buf.toString();
+  }
+
+  /// Generate an extended model class.
+  void generateClass(BuildContext ctx, FileBuilder file) {
+    file.body.add(new Class((clazz) {
+      clazz
+        ..name = ctx.modelClassNameRecase.pascalCase
+        ..extend = new Reference(ctx.originalClassName);
+
+      for (var field in ctx.fields) {
+        clazz.fields.add(new Field((b) {
+          b
+            ..name = field.name
+            ..modifier = FieldModifier.final$
+            ..annotations
+                .add(new Annotation((b) => b.code = new Code('override')))
+            ..type = convertTypeReference(field.type);
+        }));
+      }
+
+      generateConstructor(ctx, clazz, file);
+      generateCopyWithMethod(ctx, clazz, file);
+    }));
+  }
+
+  /// Generate a constructor with named parameters.
+  void generateConstructor(
+      BuildContext ctx, ClassBuilder clazz, FileBuilder file) {
+    clazz.constructors.add(new Constructor((constructor) {
+      for (var field in ctx.fields) {
+        constructor.optionalParameters.add(new Parameter((b) {
+          b
+            ..name = field.name
+            ..named = true
+            ..toThis = true;
+        }));
+      }
+    }));
+  }
+
+  /// Generate a `copyWith` method.
+  void generateCopyWithMethod(
+      BuildContext ctx, ClassBuilder clazz, FileBuilder file) {
+    clazz.methods.add(new Method((method) {
+      method
+        ..name = 'copyWith'
+        ..returns = ctx.modelClassType;
+
+      var buf = new StringBuffer('return new ${ctx.modelClassName}(');
+      int i = 0;
+
+      // Add named parameters
+      for (var field in ctx.fields) {
+        method.optionalParameters.add(new Parameter((b) {
+          b
+            ..name = field.name
+            ..named = true
+            ..type = convertTypeReference(field.type);
+        }));
+
+        if (i++ > 0) buf.write(', ');
+        buf.write('${field.name}: ${field.name} ?? this.${field.name}');
+      }
+
+      buf.write(');');
+      method.body = new Code(buf.toString());
+    }));
+  }
+}
diff --git a/angel_serialize_generator/test/models/author.dart b/angel_serialize_generator/test/models/author.dart
index 66ecac61..9a6e1716 100644
--- a/angel_serialize_generator/test/models/author.dart
+++ b/angel_serialize_generator/test/models/author.dart
@@ -3,6 +3,7 @@ library angel_serialize.test.models.author;
 import 'package:angel_framework/common.dart';
 import 'package:angel_serialize/angel_serialize.dart';
 import 'book.dart';
+
 part 'author.g.dart';
 
 @serializable
@@ -18,4 +19,4 @@ abstract class _Author extends Model {
 @serializable
 abstract class _Library extends Model {
   Map<String, Book> collection;
-}
\ No newline at end of file
+}
diff --git a/angel_serialize_generator/test/models/author.g.dart b/angel_serialize_generator/test/models/author.g.dart
index ed7c2792..b95c10ac 100644
--- a/angel_serialize_generator/test/models/author.g.dart
+++ b/angel_serialize_generator/test/models/author.g.dart
@@ -13,32 +13,79 @@ class Author extends _Author {
       this.age,
       this.books,
       this.newestBook,
+      this.secret,
       this.createdAt,
       this.updatedAt});
 
+  @override
   final String id;
 
+  @override
   final String name;
 
+  @override
   final int age;
 
+  @override
   final List<Book> books;
 
+  @override
   final Book newestBook;
 
+  @override
+  final String secret;
+
+  @override
   final DateTime createdAt;
 
+  @override
   final DateTime updatedAt;
+
+  Author copyWith(
+      {String id,
+      String name,
+      int age,
+      List<Book> books,
+      Book newestBook,
+      String secret,
+      DateTime createdAt,
+      DateTime updatedAt}) {
+    return new Author(
+        id: id ?? this.id,
+        name: name ?? this.name,
+        age: age ?? this.age,
+        books: books ?? this.books,
+        newestBook: newestBook ?? this.newestBook,
+        secret: secret ?? this.secret,
+        createdAt: createdAt ?? this.createdAt,
+        updatedAt: updatedAt ?? this.updatedAt);
+  }
 }
 
 class Library extends _Library {
   Library({this.id, this.collection, this.createdAt, this.updatedAt});
 
+  @override
   final String id;
 
+  @override
   final Map<String, Book> collection;
 
+  @override
   final DateTime createdAt;
 
+  @override
   final DateTime updatedAt;
+
+  Library copyWith(
+      {String id,
+      Map<String, Book> collection,
+      DateTime createdAt,
+      DateTime updatedAt}) {
+    return new Library(
+        id: id ?? this.id,
+        collection: collection ?? this.collection,
+        createdAt: createdAt ?? this.createdAt,
+        updatedAt: updatedAt ?? this.updatedAt);
+  }
 }
diff --git a/angel_serialize_generator/test/models/book.g.dart b/angel_serialize_generator/test/models/book.g.dart
index 100d634d..5536383b 100644
--- a/angel_serialize_generator/test/models/book.g.dart
+++ b/angel_serialize_generator/test/models/book.g.dart
@@ -16,17 +16,42 @@ class Book extends _Book {
       this.createdAt,
       this.updatedAt});
 
+  @override
   final String id;
 
+  @override
   final String author;
 
+  @override
   final String title;
 
+  @override
   final String description;
 
+  @override
   final int pageCount;
 
+  @override
   final DateTime createdAt;
 
+  @override
   final DateTime updatedAt;
+
+  Book copyWith(
+      {String id,
+      String author,
+      String title,
+      String description,
+      int pageCount,
+      DateTime createdAt,
+      DateTime updatedAt}) {
+    return new Book(
+        id: id ?? this.id,
+        author: author ?? this.author,
+        title: title ?? this.title,
+        description: description ?? this.description,
+        pageCount: pageCount ?? this.pageCount,
+        createdAt: createdAt ?? this.createdAt,
+        updatedAt: updatedAt ?? this.updatedAt);
+  }
 }