diff --git a/static/demos/light-dark-demo-4/sw.js b/static/demos/light-dark-demo-4/sw.js
index 3fd6276..8732a4f 100644
--- a/static/demos/light-dark-demo-4/sw.js
+++ b/static/demos/light-dark-demo-4/sw.js
@@ -19,7 +19,7 @@ self.addEventListener("fetch", event =>{
 })
 
 async function handle_redirect(req){
-    const url = new URL(event.request.url);
+    const url = new URL(req);
     const go_back_to = url.searchParams.get('ref') ?? '/';
     console.log("ref:",url.searchParams.get('ref'), go_back_to);
     const db_req = self.indexedDB.open("light-dark-store");