--- a/dom/media/mediasource/MediaSourceDemuxer.cpp
+++ b/dom/media/mediasource/MediaSourceDemuxer.cpp
@@ -382,18 +382,19 @@ MediaSourceTrackDemuxer::DoSeek(media::T
 {
   TimeIntervals buffered = mManager->Buffered(mType);
   buffered.SetFuzz(MediaSourceDemuxer::EOS_FUZZ);
   TimeUnit seekTime = std::max(aTime - mPreRoll, TimeUnit::FromMicroseconds(0));
 
   if (!buffered.Contains(seekTime)) {
     if (!buffered.Contains(aTime)) {
       // We don't have the data to seek to.
-      return SeekPromise::CreateAndReject(DemuxerFailureReason::WAITING_FOR_DATA,
-                                          __func__);
+      return SeekPromise::CreateAndReject(
+        mManager->IsEnded() ? DemuxerFailureReason::END_OF_STREAM :
+                              DemuxerFailureReason::WAITING_FOR_DATA, __func__);
     }
     // Theorically we should reject the promise with WAITING_FOR_DATA,
     // however, to avoid unwanted regressions we assume that if at this time
     // we don't have the wanted data it won't come later.
     // Instead of using the pre-rolled time, use the earliest time available in
     // the interval.
     TimeIntervals::IndexType index = buffered.Find(aTime);
     MOZ_ASSERT(index != TimeIntervals::NoIndex);