--- a/dom/media/MediaDecoder.h
+++ b/dom/media/MediaDecoder.h
@@ -685,23 +685,23 @@ protected:
   MediaChannelStatistics mPlaybackStatistics;
 
   // True when our media stream has been pinned. We pin the stream
   // while seeking.
   bool mPinnedForSeek;
 
   // Be assigned from media element during the initialization and pass to
   // AudioStream Class.
-  dom::AudioChannel mAudioChannel;
+  const dom::AudioChannel mAudioChannel;
 
   // True if the decoder has been directed to minimize its preroll before
   // playback starts. After the first time playback starts, we don't attempt
   // to minimize preroll, as we assume the user is likely to keep playing,
   // or play the media again.
-  bool mMinimizePreroll;
+  const bool mMinimizePreroll;
 
   // True if we've already fired metadataloaded.
   bool mFiredMetadataLoaded;
 
   // True if the media is seekable (i.e. supports random access).
   bool mMediaSeekable = true;
 
   // True if the media is only seekable within its buffered ranges