diff --git a/packages/go_router/test/go_router_test.dart b/packages/go_router/test/go_router_test.dart
index 47181b5f0e..fb1dbd71d8 100644
--- a/packages/go_router/test/go_router_test.dart
+++ b/packages/go_router/test/go_router_test.dart
@@ -689,7 +689,8 @@ void main() {
         'Handles the Android back button when parentNavigatorKey is set to the root navigator',
         (WidgetTester tester) async {
       final List<MethodCall> log = <MethodCall>[];
-      TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger
+      _ambiguate(TestDefaultBinaryMessengerBinding.instance)!
+          .defaultBinaryMessenger
           .setMockMethodCallHandler(SystemChannels.platform,
               (MethodCall methodCall) async {
         log.add(methodCall);
@@ -731,7 +732,8 @@ void main() {
     testWidgets("Handles the Android back button when ShellRoute can't pop",
         (WidgetTester tester) async {
       final List<MethodCall> log = <MethodCall>[];
-      TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger
+      _ambiguate(TestDefaultBinaryMessengerBinding.instance)!
+          .defaultBinaryMessenger
           .setMockMethodCallHandler(SystemChannels.platform,
               (MethodCall methodCall) async {
         log.add(methodCall);
@@ -795,7 +797,8 @@ void main() {
       'Handles the Android back button when a second Shell has a GoRoute with parentNavigator key',
       (WidgetTester tester) async {
     final List<MethodCall> log = <MethodCall>[];
-    TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger
+    _ambiguate(TestDefaultBinaryMessengerBinding.instance)!
+        .defaultBinaryMessenger
         .setMockMethodCallHandler(SystemChannels.platform,
             (MethodCall methodCall) async {
       log.add(methodCall);
@@ -884,7 +887,8 @@ void main() {
   group('report correct url', () {
     final List<MethodCall> log = <MethodCall>[];
     setUp(() {
-      TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger
+      _ambiguate(TestDefaultBinaryMessengerBinding.instance)!
+          .defaultBinaryMessenger
           .setMockMethodCallHandler(SystemChannels.navigation,
               (MethodCall methodCall) async {
         log.add(methodCall);
@@ -892,7 +896,8 @@ void main() {
       });
     });
     tearDown(() {
-      TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger
+      _ambiguate(TestDefaultBinaryMessengerBinding.instance)!
+          .defaultBinaryMessenger
           .setMockMethodCallHandler(SystemChannels.navigation, null);
       log.clear();
     });
@@ -3271,3 +3276,9 @@ void main() {
     });
   });
 }
+
+/// This allows a value of type T or T? to be treated as a value of type T?.
+///
+/// We use this so that APIs that have become non-nullable can still be used
+/// with `!` and `?` on the stable branch.
+T? _ambiguate<T>(T? value) => value;