diff --git a/modules/openapi-generator/src/main/resources/dart-dio/api.mustache b/modules/openapi-generator/src/main/resources/dart-dio/api.mustache
index a7618c5f72e..58fd56baac9 100644
--- a/modules/openapi-generator/src/main/resources/dart-dio/api.mustache
+++ b/modules/openapi-generator/src/main/resources/dart-dio/api.mustache
@@ -23,14 +23,14 @@ class {{classname}} {
         {{{dataType}}} {{paramName}},{{#-last}} { {{/-last}}{{/requiredParams}}{{#optionalParams}}
         {{{dataType}}} {{paramName}},{{/optionalParams}}
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '{{{path}}}'{{#pathParams}}.replaceAll('{' r'{{baseName}}' '}', {{{paramName}}}.toString()){{/pathParams}};
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         {{#headerParams}}
diff --git a/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/pet_api.dart b/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/pet_api.dart
index e9f06fdf425..0c71ae0e8e6 100644
--- a/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/pet_api.dart
@@ -21,14 +21,14 @@ class PetApi {
     Future<Response<void>> addPet(
         Pet body, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -73,14 +73,14 @@ class PetApi {
         int petId, { 
         String apiKey,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         headerParams[r'api_key'] = apiKey;
@@ -118,14 +118,14 @@ class PetApi {
     Future<Response<BuiltList<Pet>>> findPetsByStatus(
         BuiltList<String> status, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/findByStatus';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'status'] = status;
@@ -177,14 +177,14 @@ class PetApi {
     Future<Response<BuiltList<Pet>>> findPetsByTags(
         BuiltList<String> tags, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/findByTags';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'tags'] = tags;
@@ -236,14 +236,14 @@ class PetApi {
     Future<Response<Pet>> getPetById(
         int petId, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -295,14 +295,14 @@ class PetApi {
     Future<Response<void>> updatePet(
         Pet body, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -348,14 +348,14 @@ class PetApi {
         String name,
         String status,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -401,14 +401,14 @@ class PetApi {
         String additionalMetadata,
         Uint8List file,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}/uploadImage'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/store_api.dart b/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/store_api.dart
index a88515706b3..2d6820a6ff4 100644
--- a/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/store_api.dart
+++ b/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/store_api.dart
@@ -18,14 +18,14 @@ class StoreApi {
     Future<Response<void>> deleteOrder(
         String orderId, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/order/{orderId}'.replaceAll('{' r'orderId' '}', orderId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -56,14 +56,14 @@ class StoreApi {
     /// Returns a map of status codes to quantities
     Future<Response<BuiltMap<String, int>>> getInventory({ 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/inventory';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -116,14 +116,14 @@ class StoreApi {
     Future<Response<Order>> getOrderById(
         int orderId, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/order/{orderId}'.replaceAll('{' r'orderId' '}', orderId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -168,14 +168,14 @@ class StoreApi {
     Future<Response<Order>> placeOrder(
         Order body, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/order';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/user_api.dart b/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/user_api.dart
index 25bb52f6d3f..8c89c0bf370 100644
--- a/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/client/petstore/dart-dio/petstore_client_lib/lib/api/user_api.dart
@@ -18,14 +18,14 @@ class UserApi {
     Future<Response<void>> createUser(
         User body, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -61,14 +61,14 @@ class UserApi {
     Future<Response<void>> createUsersWithArrayInput(
         BuiltList<User> body, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/createWithArray';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -105,14 +105,14 @@ class UserApi {
     Future<Response<void>> createUsersWithListInput(
         BuiltList<User> body, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/createWithList';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -149,14 +149,14 @@ class UserApi {
     Future<Response<void>> deleteUser(
         String username, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/{username}'.replaceAll('{' r'username' '}', username.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -188,14 +188,14 @@ class UserApi {
     Future<Response<User>> getUserByName(
         String username, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/{username}'.replaceAll('{' r'username' '}', username.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -241,14 +241,14 @@ class UserApi {
         String username,
         String password, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/login';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'username'] = username;
@@ -293,14 +293,14 @@ class UserApi {
     /// 
     Future<Response<void>> logoutUser({ 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/logout';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -333,14 +333,14 @@ class UserApi {
         String username,
         User body, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/{username}'.replaceAll('{' r'username' '}', username.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/pet_api.dart
index 3874a0993d6..e74ee3f940f 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/pet_api.dart
@@ -21,14 +21,14 @@ class PetApi {
     Future<Response<Pet>> addPet(
         Pet pet, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -86,14 +86,14 @@ class PetApi {
         int petId, { 
         String apiKey,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         headerParams[r'api_key'] = apiKey;
@@ -131,14 +131,14 @@ class PetApi {
     Future<Response<BuiltList<Pet>>> findPetsByStatus(
         BuiltList<String> status, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/findByStatus';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'status'] = status;
@@ -190,14 +190,14 @@ class PetApi {
     Future<Response<BuiltList<Pet>>> findPetsByTags(
         BuiltList<String> tags, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/findByTags';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'tags'] = tags;
@@ -249,14 +249,14 @@ class PetApi {
     Future<Response<Pet>> getPetById(
         int petId, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -308,14 +308,14 @@ class PetApi {
     Future<Response<Pet>> updatePet(
         Pet pet, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -374,14 +374,14 @@ class PetApi {
         String name,
         String status,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -427,14 +427,14 @@ class PetApi {
         String additionalMetadata,
         Uint8List file,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}/uploadImage'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/store_api.dart
index 24c20b20a00..a5c1fb5a798 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/store_api.dart
@@ -18,14 +18,14 @@ class StoreApi {
     Future<Response<void>> deleteOrder(
         String orderId, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/order/{orderId}'.replaceAll('{' r'orderId' '}', orderId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -56,14 +56,14 @@ class StoreApi {
     /// Returns a map of status codes to quantities
     Future<Response<BuiltMap<String, int>>> getInventory({ 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/inventory';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -116,14 +116,14 @@ class StoreApi {
     Future<Response<Order>> getOrderById(
         int orderId, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/order/{orderId}'.replaceAll('{' r'orderId' '}', orderId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -168,14 +168,14 @@ class StoreApi {
     Future<Response<Order>> placeOrder(
         Order order, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/order';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/user_api.dart
index 8465f56a8f0..d8abb0867e2 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib/lib/api/user_api.dart
@@ -18,14 +18,14 @@ class UserApi {
     Future<Response<void>> createUser(
         User user, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -70,14 +70,14 @@ class UserApi {
     Future<Response<void>> createUsersWithArrayInput(
         BuiltList<User> user, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/createWithArray';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -123,14 +123,14 @@ class UserApi {
     Future<Response<void>> createUsersWithListInput(
         BuiltList<User> user, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/createWithList';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -176,14 +176,14 @@ class UserApi {
     Future<Response<void>> deleteUser(
         String username, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/{username}'.replaceAll('{' r'username' '}', username.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -222,14 +222,14 @@ class UserApi {
     Future<Response<User>> getUserByName(
         String username, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/{username}'.replaceAll('{' r'username' '}', username.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -275,14 +275,14 @@ class UserApi {
         String username,
         String password, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/login';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'username'] = username;
@@ -327,14 +327,14 @@ class UserApi {
     /// 
     Future<Response<void>> logoutUser({ 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/logout';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -374,14 +374,14 @@ class UserApi {
         String username,
         User user, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/{username}'.replaceAll('{' r'username' '}', username.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/another_fake_api.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/another_fake_api.dart
index 84561eaab29..5fc9460a253 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/another_fake_api.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/another_fake_api.dart
@@ -17,14 +17,14 @@ class AnotherFakeApi {
     Future<Response<Client>> call123testSpecialTags(
         Client client, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/another-fake/dummy';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/default_api.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/default_api.dart
index 793adab0628..7d13a5522cc 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/default_api.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/default_api.dart
@@ -16,14 +16,14 @@ class DefaultApi {
     /// 
     Future<Response<InlineResponseDefault>> fooGet({ 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/foo';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/fake_api.dart
index 0ae212b39e0..1ae970f0e96 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/fake_api.dart
@@ -24,14 +24,14 @@ class FakeApi {
     /// 
     Future<Response<HealthCheckResult>> fakeHealthGet({ 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/health';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -78,14 +78,14 @@ class FakeApi {
         String query1,
         String header1,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/http-signature-test';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         headerParams[r'header_1'] = header1;
@@ -131,14 +131,14 @@ class FakeApi {
     Future<Response<bool>> fakeOuterBooleanSerialize({ 
         bool body,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/outer/boolean';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -188,14 +188,14 @@ class FakeApi {
     Future<Response<OuterComposite>> fakeOuterCompositeSerialize({ 
         OuterComposite outerComposite,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/outer/composite';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -246,14 +246,14 @@ class FakeApi {
     Future<Response<num>> fakeOuterNumberSerialize({ 
         num body,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/outer/number';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -303,14 +303,14 @@ class FakeApi {
     Future<Response<String>> fakeOuterStringSerialize({ 
         String body,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/outer/string';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -360,14 +360,14 @@ class FakeApi {
     Future<Response<void>> testBodyWithFileSchema(
         FileSchemaTestClass fileSchemaTestClass, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/body-with-file-schema';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -406,14 +406,14 @@ class FakeApi {
         String query,
         User user, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/body-with-query-params';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'query'] = query;
@@ -452,14 +452,14 @@ class FakeApi {
     Future<Response<Client>> testClientModel(
         Client client, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -523,14 +523,14 @@ class FakeApi {
         String password,
         String callback,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -593,14 +593,14 @@ class FakeApi {
         BuiltList<String> enumFormStringArray,
         String enumFormString,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         headerParams[r'enum_header_string_array'] = enumHeaderStringArray;
@@ -650,14 +650,14 @@ class FakeApi {
         bool booleanGroup,
         int int64Group,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         headerParams[r'required_boolean_group'] = requiredBooleanGroup;
@@ -700,14 +700,14 @@ class FakeApi {
     Future<Response<void>> testInlineAdditionalProperties(
         BuiltMap<String, String> requestBody, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/inline-additionalProperties';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -746,14 +746,14 @@ class FakeApi {
         String param,
         String param2, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/jsonFormData';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -796,14 +796,14 @@ class FakeApi {
         BuiltList<String> url,
         BuiltList<String> context, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/test-query-paramters';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'pipe'] = pipe;
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
index 3b4ae19dee1..d0bb38311f5 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
@@ -17,14 +17,14 @@ class FakeClassnameTags123Api {
     Future<Response<Client>> testClassname(
         Client client, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake_classname_test';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/pet_api.dart
index 6ef0ef3919a..7bc7b217fa1 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/pet_api.dart
@@ -21,14 +21,14 @@ class PetApi {
     Future<Response<void>> addPet(
         Pet pet, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -73,14 +73,14 @@ class PetApi {
         int petId, { 
         String apiKey,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         headerParams[r'api_key'] = apiKey;
@@ -118,14 +118,14 @@ class PetApi {
     Future<Response<BuiltList<Pet>>> findPetsByStatus(
         BuiltList<String> status, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/findByStatus';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'status'] = status;
@@ -177,14 +177,14 @@ class PetApi {
     Future<Response<BuiltList<Pet>>> findPetsByTags(
         BuiltList<String> tags, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/findByTags';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'tags'] = tags;
@@ -236,14 +236,14 @@ class PetApi {
     Future<Response<Pet>> getPetById(
         int petId, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -295,14 +295,14 @@ class PetApi {
     Future<Response<void>> updatePet(
         Pet pet, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -348,14 +348,14 @@ class PetApi {
         String name,
         String status,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -401,14 +401,14 @@ class PetApi {
         String additionalMetadata,
         Uint8List file,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/pet/{petId}/uploadImage'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -471,14 +471,14 @@ class PetApi {
         Uint8List requiredFile, { 
         String additionalMetadata,
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/fake/{petId}/uploadImageWithRequiredFile'.replaceAll('{' r'petId' '}', petId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/store_api.dart
index 5158a31a685..89f845eea20 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/store_api.dart
@@ -18,14 +18,14 @@ class StoreApi {
     Future<Response<void>> deleteOrder(
         String orderId, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/order/{order_id}'.replaceAll('{' r'order_id' '}', orderId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -56,14 +56,14 @@ class StoreApi {
     /// Returns a map of status codes to quantities
     Future<Response<BuiltMap<String, int>>> getInventory({ 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/inventory';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -116,14 +116,14 @@ class StoreApi {
     Future<Response<Order>> getOrderById(
         int orderId, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/order/{order_id}'.replaceAll('{' r'order_id' '}', orderId.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -168,14 +168,14 @@ class StoreApi {
     Future<Response<Order>> placeOrder(
         Order order, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/store/order';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/user_api.dart
index b7ae8fb8648..3e2d4936a18 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/api/user_api.dart
@@ -18,14 +18,14 @@ class UserApi {
     Future<Response<void>> createUser(
         User user, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -63,14 +63,14 @@ class UserApi {
     Future<Response<void>> createUsersWithArrayInput(
         BuiltList<User> user, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/createWithArray';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -109,14 +109,14 @@ class UserApi {
     Future<Response<void>> createUsersWithListInput(
         BuiltList<User> user, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/createWithList';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -155,14 +155,14 @@ class UserApi {
     Future<Response<void>> deleteUser(
         String username, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/{username}'.replaceAll('{' r'username' '}', username.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -194,14 +194,14 @@ class UserApi {
     Future<Response<User>> getUserByName(
         String username, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/{username}'.replaceAll('{' r'username' '}', username.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -247,14 +247,14 @@ class UserApi {
         String username,
         String password, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/login';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams[r'username'] = username;
@@ -299,14 +299,14 @@ class UserApi {
     /// 
     Future<Response<void>> logoutUser({ 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/logout';
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);
@@ -339,14 +339,14 @@ class UserApi {
         String username,
         User user, { 
         CancelToken cancelToken,
-        Map<String, String> headers,
+        Map<String, dynamic> headers,
         ProgressCallback onSendProgress,
         ProgressCallback onReceiveProgress,
     }) async {
         final String _path = '/user/{username}'.replaceAll('{' r'username' '}', username.toString());
 
         final Map<String, dynamic> queryParams = {};
-        final Map<String, String> headerParams = Map.from(headers ?? {});
+        final Map<String, dynamic> headerParams = Map.from(headers ?? {});
         dynamic bodyData;
 
         queryParams.removeWhere((key, value) => value == null);