--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -1387,16 +1387,17 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_
   }
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPlayed);
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mTextTrackManager)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mAudioTrackList)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mVideoTrackList)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mMediaKeys)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSelectedVideoStreamTrack)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPendingPlayPromises)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSeekDOMPromise)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(HTMLMediaElement, nsGenericHTMLElement)
   if (tmp->mSrcStream) {
     // Need to EndMediaStreamPlayback to clear mSrcStream and make sure everything
     // gets unhooked correctly.
     tmp->EndSrcMediaStreamPlayback();
   }
@@ -1416,16 +1417,17 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_IN
   }
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mPlayed)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mTextTrackManager)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mAudioTrackList)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mVideoTrackList)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mMediaKeys)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mSelectedVideoStreamTrack)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mPendingPlayPromises)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mSeekDOMPromise)
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(HTMLMediaElement)
   NS_INTERFACE_MAP_ENTRY(nsIDOMHTMLMediaElement)
 NS_INTERFACE_MAP_END_INHERITING(nsGenericHTMLElement)
 
 // nsIDOMHTMLMediaElement
 NS_IMPL_URI_ATTR(HTMLMediaElement, Src, src)