diff --git a/examples/zkapps/04-zkapp-browser-ui/ui/src/pages/zkappWorker.ts b/examples/zkapps/04-zkapp-browser-ui/ui/src/pages/zkappWorker.ts
index 793ff194b..795c1d352 100644
--- a/examples/zkapps/04-zkapp-browser-ui/ui/src/pages/zkappWorker.ts
+++ b/examples/zkapps/04-zkapp-browser-ui/ui/src/pages/zkappWorker.ts
@@ -71,7 +71,7 @@ export type ZkappWorkerReponse = {
   id: number;
   data: any;
 };
-if (process.browser) {
+if (typeof window !== 'undefined') {
   addEventListener(
     'message',
     async (event: MessageEvent<ZkappWorkerRequest>) => {