Fixes #6046
@ -40,7 +40,7 @@ class EmbedThumbnailPP(FFmpegPostProcessor):
'Skipping embedding the thumbnail because the file is missing.')
return [], info
if info['ext'] == 'mp3':
if info['ext'] in ('mp3', 'mkv'):
options = [
'-c', 'copy', '-map', '0', '-map', '1',
'-metadata:s:v', 'title="Album cover"', '-metadata:s:v', 'comment="Cover (Front)"']