--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -5712,19 +5712,19 @@ HTMLMediaElement::CheckProgress(bool aHa
       }
     }
     // Download statistics may have been updated, force a recheck of the
     // readyState.
     UpdateReadyStateInternal();
   }
 
   if (now - mDataTime >= TimeDuration::FromMilliseconds(STALL_MS)) {
-    DispatchAsyncEvent(NS_LITERAL_STRING("stalled"));
-
-    if (mMediaSource) {
+    if (!mMediaSource) {
+      DispatchAsyncEvent(NS_LITERAL_STRING("stalled"));
+    } else {
       ChangeDelayLoadStatus(false);
     }
 
     NS_ASSERTION(mProgressTimer, "detected stalled without timer");
     // Stop timer events, which prevents repeated stalled events until there
     // is more progress.
     StopProgress();
   }

--- a/dom/media/mediasource/test/test_ChangeWhileWaitingOnMissingData_mp4.html
+++ b/dom/media/mediasource/test/test_ChangeWhileWaitingOnMissingData_mp4.html
@@ -18,17 +18,17 @@ runWithMSE(function(ms, el) {
     const sb = ms.addSourceBuffer("video/mp4");
     fetchAndLoad(sb, "bipbop/bipbop_480_624kbps-video", [ "init" ], ".mp4")
     .then(fetchAndLoad.bind(null, sb, "bipbop/bipbop_480_624kbps-video", range(1, 3), ".m4s"))
     .then(function() {
       el.play();
       // let seek to the last audio frame.
       // The seek will complete and then playback will stall.
       el.currentTime = 1.532517;
-      return Promise.all([ once(el, "seeked"), once(el, "stalled") ]);
+      return Promise.all([ once(el, "seeked"), once(el, "waiting") ]);
     })
     .then(function() {
       info("seek completed");
       return fetchAndLoad(sb, "bipbop/bipbop", [ "init" ], ".mp4");
     })
     .then(fetchAndLoad.bind(null, sb, "bipbop/bipbop", range(1, 4), ".m4s"))
     .then(function() {
       ms.endOfStream();