diff --git a/lib/web_ui/test/engine/clipboard_test.dart b/lib/web_ui/test/engine/clipboard_test.dart
index 097cf855d1eda..bad7902156ca6 100644
--- a/lib/web_ui/test/engine/clipboard_test.dart
+++ b/lib/web_ui/test/engine/clipboard_test.dart
@@ -58,7 +58,7 @@ Future<void> testMain() async {
       const MethodCodec codec = JSONMethodCodec();
       final Completer<ByteData> completer = Completer<ByteData>();
       void callback(ByteData? data) {
-        completer.complete(data);
+        completer.complete(data!);
       }
 
       clipboardMessageHandler.setDataMethodCall(