diff --git a/packages/flutter_tools/lib/src/web/devfs_web.dart b/packages/flutter_tools/lib/src/web/devfs_web.dart
index 30cf9e41a7b..cf795ae7fd3 100644
--- a/packages/flutter_tools/lib/src/web/devfs_web.dart
+++ b/packages/flutter_tools/lib/src/web/devfs_web.dart
@@ -352,12 +352,12 @@ class WebDevFS implements DevFS {
           generateBootstrapScript(
             requireUrl: _filePathToUriFragment(requireJS.path),
             mapperUrl: _filePathToUriFragment(stackTraceMapper.path),
-            entrypoint: '${_filePathToUriFragment(mainPath)}.js',
+            entrypoint: '${_filePathToUriFragment(mainPath)}.lib.js',
           ));
       _webAssetServer.writeFile(
           '/main_module.js',
           generateMainModule(
-            entrypoint: '${_filePathToUriFragment(mainPath)}.js',
+            entrypoint: '${_filePathToUriFragment(mainPath)}.lib.js',
           ));
       _webAssetServer.writeFile('/dart_sdk.js', dartSdk.readAsStringSync());
       _webAssetServer.writeFile(