diff --git a/chopper/lib/src/base.dart b/chopper/lib/src/base.dart
index d936c669..ff4bb051 100644
--- a/chopper/lib/src/base.dart
+++ b/chopper/lib/src/base.dart
@@ -340,7 +340,7 @@ class ChopperClient {
     Map<String, String> headers = const {},
     Map<String, dynamic> parameters = const {},
     String? baseUrl,
-    dynamic? body,
+    dynamic body,
   }) =>
       send<BodyType, InnerType>(
         Request(
diff --git a/chopper_generator/lib/chopper_generator.dart b/chopper_generator/lib/chopper_generator.dart
index e19b3343..2facc8b0 100644
--- a/chopper_generator/lib/chopper_generator.dart
+++ b/chopper_generator/lib/chopper_generator.dart
@@ -4,4 +4,4 @@ import 'package:build/build.dart';
 import 'src/generator.dart';
 
 Builder chopperGeneratorFactory(BuilderOptions options) =>
-    chopperGeneratorFactoryBuilder(header: options.config['header'] as String);
+    chopperGeneratorFactoryBuilder(header: options.config['header']);
diff --git a/chopper_generator/lib/src/generator.dart b/chopper_generator/lib/src/generator.dart
index 1ad77a42..cadcfcbc 100644
--- a/chopper_generator/lib/src/generator.dart
+++ b/chopper_generator/lib/src/generator.dart
@@ -503,7 +503,7 @@ class ChopperGenerator extends GeneratorForAnnotation<chopper.ChopperApi> {
   }
 }
 
-Builder chopperGeneratorFactoryBuilder({String header = ''}) => PartBuilder(
+Builder chopperGeneratorFactoryBuilder({String? header}) => PartBuilder(
       [ChopperGenerator()],
       '.chopper.dart',
       header: header,