--- a/browser/base/content/test/webrtc/browser_devices_get_user_media_unprompted_access_tear_off_tab.js
+++ b/browser/base/content/test/webrtc/browser_devices_get_user_media_unprompted_access_tear_off_tab.js
@@ -26,16 +26,17 @@ var gTests = [
     Assert.deepEqual((yield getMediaCaptureState()), {audio: true, video: true},
                      "expected camera and microphone to be shared");
 
     yield indicator;
     yield checkSharingUI({video: true, audio: true});
 
     info("tearing off the tab");
     let win = gBrowser.replaceTabWithWindow(gBrowser.selectedTab);
+    yield new Promise(resolve => waitForFocus(resolve, win));
     yield whenDelayedStartupFinished(win);
     yield checkSharingUI({audio: true, video: true}, win);
 
     gBrowser.selectedBrowser.messageManager.loadFrameScript(CONTENT_SCRIPT_HELPER, true);
 
     info("request audio+video and check if there is no prompt");
     yield promiseRequestDevice(true, true, null, null, win.gBrowser.selectedBrowser);
     yield promiseObserverCalled("getUserMedia:request");