--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -2215,28 +2215,31 @@ SeekingState::SeekCompleted()
 
     // We won't start MediaSink when paused. m{Audio,Video}Completed will
     // remain false and 'playbackEnded' won't be notified. Therefore we
     // need to set these flags explicitly when seeking to the end.
     mMaster->mAudioCompleted = true;
     mMaster->mVideoCompleted = true;
   }
 
+  // Cache mTarget for mSeekJob.Resolve() below will reset it.
+  SeekTarget target = mSeekJob.mTarget.ref();
+
   // We want to resolve the seek request prior finishing the first frame
   // to ensure that the seeked event is fired prior loadeded.
   mSeekJob.Resolve(__func__);
 
   // Notify FirstFrameLoaded now if we haven't since we've decoded some data
   // for readyState to transition to HAVE_CURRENT_DATA and fire 'loadeddata'.
   if (!mMaster->mSentFirstFrameLoadedEvent) {
     mMaster->FinishDecodeFirstFrame();
   }
 
   // Ensure timestamps are up to date.
-  if (!mSeekJob.mTarget->IsVideoOnly()) {
+  if (!target.IsVideoOnly()) {
     // Don't update playback position for video-only seek.
     // Otherwise we might have |newCurrentTime > mMediaSink->GetPosition()|
     // and fail the assertion in GetClock() since we didn't stop MediaSink.
     mMaster->UpdatePlaybackPositionInternal(newCurrentTime);
   }
 
   // Try to decode another frame to detect if we're at the end...
   SLOG("Seek completed, mCurrentPosition=%lld", mMaster->mCurrentPosition.Ref());