diff --git a/pkg/analysis_server/test/lsp/initialization_test.dart b/pkg/analysis_server/test/lsp/initialization_test.dart
index aa19b1d..e06c249 100644
--- a/pkg/analysis_server/test/lsp/initialization_test.dart
+++ b/pkg/analysis_server/test/lsp/initialization_test.dart
@@ -170,6 +170,7 @@
       const Duration(seconds: 1),
       onTimeout: () {
         didTimeout = true;
+        return null;
       },
     );
 
diff --git a/pkg/analysis_server/test/lsp/server_test.dart b/pkg/analysis_server/test/lsp/server_test.dart
index eb79236..17cea13 100644
--- a/pkg/analysis_server/test/lsp/server_test.dart
+++ b/pkg/analysis_server/test/lsp/server_test.dart
@@ -75,6 +75,7 @@
       const Duration(seconds: 1),
       onTimeout: () {
         didTimeout = true;
+        return null;
       },
     );