diff --git a/beetsplug/scrub.py b/beetsplug/scrub.py
index 317687318..ddd7fd0cc 100644
--- a/beetsplug/scrub.py
+++ b/beetsplug/scrub.py
@@ -31,6 +31,7 @@ _MUTAGEN_FORMATS = {
     'flac': 'FLAC',
     'id3': 'ID3FileType',
     'mp3': 'MP3',
+    'mp4': 'MP4',
     'oggflac': 'OggFLAC',
     'oggspeex': 'OggSpeex',
     'oggtheora': 'OggTheora',