diff --git a/.dart_tool/package_config.json b/.dart_tool/package_config.json
index fa954aedb81..d7bbb3864f7 100644
--- a/.dart_tool/package_config.json
+++ b/.dart_tool/package_config.json
@@ -326,7 +326,7 @@
       "name": "frontend_server",
       "rootUri": "../pkg/frontend_server",
       "packageUri": "lib/",
-      "languageVersion": "2.7"
+      "languageVersion": "2.15"
     },
     {
       "name": "frontend_server_client",
diff --git a/pkg/frontend_server/bin/frontend_server_starter.dart b/pkg/frontend_server/bin/frontend_server_starter.dart
index 2113752afdd..82b6fb82c04 100644
--- a/pkg/frontend_server/bin/frontend_server_starter.dart
+++ b/pkg/frontend_server/bin/frontend_server_starter.dart
@@ -1,3 +1,4 @@
+// @dart = 2.9
 library frontend_server;
 
 import 'dart:async';
diff --git a/pkg/frontend_server/lib/frontend_server.dart b/pkg/frontend_server/lib/frontend_server.dart
index bcfd7995f2a..a9fe7ddd85f 100644
--- a/pkg/frontend_server/lib/frontend_server.dart
+++ b/pkg/frontend_server/lib/frontend_server.dart
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.9
 library frontend_server;
 
 import 'dart:async';
diff --git a/pkg/frontend_server/lib/src/javascript_bundle.dart b/pkg/frontend_server/lib/src/javascript_bundle.dart
index d39ee754190..00ddccb7d66 100644
--- a/pkg/frontend_server/lib/src/javascript_bundle.dart
+++ b/pkg/frontend_server/lib/src/javascript_bundle.dart
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.9
 import 'dart:convert';
 import 'dart:io';
 
diff --git a/pkg/frontend_server/lib/src/strong_components.dart b/pkg/frontend_server/lib/src/strong_components.dart
index 4c010a8eba8..0711f2d95e9 100644
--- a/pkg/frontend_server/lib/src/strong_components.dart
+++ b/pkg/frontend_server/lib/src/strong_components.dart
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.9
 import 'package:kernel/ast.dart';
 import 'package:kernel/util/graph.dart';
 
diff --git a/pkg/frontend_server/pubspec.yaml b/pkg/frontend_server/pubspec.yaml
index 9985e929e28..62f7446eaa4 100644
--- a/pkg/frontend_server/pubspec.yaml
+++ b/pkg/frontend_server/pubspec.yaml
@@ -4,7 +4,7 @@ description: A resident kernel compiler
 publish_to: none
 
 environment:
-  sdk: "^2.7.0"
+  sdk: "^2.15.0"
 
 dependencies:
   args: ^2.0.0
diff --git a/pkg/frontend_server/test/frontend_server_flutter.dart b/pkg/frontend_server/test/frontend_server_flutter.dart
index 78c9a7ba9d7..e0132b33666 100644
--- a/pkg/frontend_server/test/frontend_server_flutter.dart
+++ b/pkg/frontend_server/test/frontend_server_flutter.dart
@@ -1,3 +1,4 @@
+// @dart = 2.9
 import 'dart:async' show StreamController;
 import 'dart:convert' show utf8, LineSplitter;
 import 'dart:io' show Directory, File, FileSystemEntity, IOSink, exitCode;
diff --git a/pkg/frontend_server/test/frontend_server_flutter_suite.dart b/pkg/frontend_server/test/frontend_server_flutter_suite.dart
index 36ae5617cf2..0a6b249af9d 100644
--- a/pkg/frontend_server/test/frontend_server_flutter_suite.dart
+++ b/pkg/frontend_server/test/frontend_server_flutter_suite.dart
@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
+// @dart = 2.9
 import 'dart:async' show StreamSubscription, Timer;
 import 'dart:convert' show jsonEncode;
 import 'dart:io' show File, exitCode;
diff --git a/pkg/frontend_server/test/frontend_server_test.dart b/pkg/frontend_server/test/frontend_server_test.dart
index 1d7e607b5ba..d34b0674eb0 100644
--- a/pkg/frontend_server/test/frontend_server_test.dart
+++ b/pkg/frontend_server/test/frontend_server_test.dart
@@ -1,3 +1,4 @@
+// @dart = 2.9
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
diff --git a/pkg/frontend_server/test/src/javascript_bundle_test.dart b/pkg/frontend_server/test/src/javascript_bundle_test.dart
index 69a7156fe68..488e986001f 100644
--- a/pkg/frontend_server/test/src/javascript_bundle_test.dart
+++ b/pkg/frontend_server/test/src/javascript_bundle_test.dart
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.9
 import 'dart:convert';
 import 'dart:io';
 
diff --git a/pkg/frontend_server/test/src/strong_components_test.dart b/pkg/frontend_server/test/src/strong_components_test.dart
index 9bb6596c6b9..2281e82cfc7 100644
--- a/pkg/frontend_server/test/src/strong_components_test.dart
+++ b/pkg/frontend_server/test/src/strong_components_test.dart
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.9
 import 'package:frontend_server/src/strong_components.dart';
 import 'package:kernel/ast.dart';
 import 'package:test/test.dart';