--- a/devtools/server/actors/tab.js
+++ b/devtools/server/actors/tab.js
@@ -1639,17 +1639,17 @@ DebuggerProgressListener.prototype = {
       if (request.status != Cr.NS_OK) {
         // Instead, listen for DOMContentLoaded as about:neterror is loaded
         // with LOAD_BACKGROUND flags and never dispatches load event.
         // That may be the same reason why there is no onStateChange event
         // for about:neterror loads.
         let handler = getDocShellChromeEventHandler(progress);
         let onLoad = evt => {
           // Ignore events from iframes
-          if (evt.target == window.document) {
+          if (!Cu.isDeadWrapper(window) && evt.target === window.document) {
             handler.removeEventListener("DOMContentLoaded", onLoad, true);
             this._tabActor._navigate(window);
           }
         };
         handler.addEventListener("DOMContentLoaded", onLoad, true);
       } else {
         // Somewhat equivalent of load event.
         // (window.document.readyState == complete)