diff --git a/extensions/amp-iframe/1.0/component.js b/extensions/amp-iframe/1.0/component.js
index a1a6e2561ebc1..c5c567cb1bee7 100644
--- a/extensions/amp-iframe/1.0/component.js
+++ b/extensions/amp-iframe/1.0/component.js
@@ -72,7 +72,9 @@ export function BentoIframe({
 
   useEffect(() => {
     const iframe = iframeRef.current;
-    if (!iframe) {
+    // TODO(36239): Ensure that effects are properly isolated between test runs.
+    // Guarding for iframe truthiness should be enough.
+    if (!iframe?.ownerDocument.defaultView) {
       return;
     }
     const win = toWin(iframe.ownerDocument.defaultView);