diff --git a/lib/builder-webpack4/src/preview/iframe-webpack.config.ts b/lib/builder-webpack4/src/preview/iframe-webpack.config.ts
index 047ace12673..66c2fbee4de 100644
--- a/lib/builder-webpack4/src/preview/iframe-webpack.config.ts
+++ b/lib/builder-webpack4/src/preview/iframe-webpack.config.ts
@@ -257,7 +257,7 @@ export default async (options: Options & Record<string, any>): Promise<Configura
       },
       runtimeChunk: true,
       sideEffects: true,
-      usedExports: isProd,
+      usedExports: true,
       moduleIds: 'named',
       minimizer: isProd
         ? [