diff --git a/webcodecs/videoFrame-serialization.crossAgentCluster.https.html b/webcodecs/videoFrame-serialization.crossAgentCluster.https.html
index e07f61072dd41cd..1266869783ded7e 100644
--- a/webcodecs/videoFrame-serialization.crossAgentCluster.https.html
+++ b/webcodecs/videoFrame-serialization.crossAgentCluster.https.html
@@ -16,14 +16,17 @@
     };
   </script>
   <script id='sharedWorkerCode' type='javascript/worker'>
+    let received = new Map();
     self.onconnect = function (event) {
       const port = event.ports[0];
       port.onmessage = function (e) {
-        let frame = e.data.frame;
-        if (e.data.transfer) {
-          port.postMessage(frame, [frame]);
-        } else {
-          port.postMessage(frame);
+        if (e.data.hasOwnProperty('id')) {
+          port.postMessage(
+            received.get(e.data.id) ? 'RECEIVED' : 'NOT_RECEIVED');
+          return;
+        }
+        if (e.data.toString() == '[object VideoFrame]') {
+          received.set(e.data.timestamp, e.data);
         }
       };
     };
@@ -70,12 +73,12 @@
   const worker = new SharedWorker(window.URL.createObjectURL(blob));
   let frame = createVideoFrame(40);
   worker.port.postMessage({frame: frame, transfer: false});
+  worker.port.postMessage({'id': 40});
   const received = await new Promise(resolve => worker.port.onmessage = e => {
     resolve(e.data);
   });
-  assert_equals(received.toString(), '[object VideoFrame]');
-  assert_equals(received.timestamp, 40);
-}, 'Verify frames can be passed back and forth between main and sharedworker');
+  assert_equals(received, 'NOT_RECEIVED');
+}, 'Verify frames cannot be passed to sharedworker');
 
 promise_test(async () => {
   navigator.serviceWorker.register('videoFrame-serialization.crossAgentCluster.serviceworker.js');
@@ -124,12 +127,12 @@
   const worker = new SharedWorker(window.URL.createObjectURL(blob));
   let frame = createVideoFrame(90);
   worker.port.postMessage({frame: frame, transfer: true});
+  worker.port.postMessage({'id': 90});
   const received = await new Promise(resolve => worker.port.onmessage = e => {
     resolve(e.data);
   });
-  assert_equals(received.toString(), '[object VideoFrame]');
-  assert_equals(received.timestamp, 90);
-}, 'Verify frames can be transferred back and forth between main and sharedworker');
+  assert_equals(received, 'NOT_RECEIVED');
+}, 'Verify frames cannot be transferred to a sharedworker');
 
 promise_test(async () => {
   navigator.serviceWorker.register('videoFrame-serialization.crossAgentCluster.serviceworker.js');