diff --git a/youtube-dl b/youtube-dl
index 71bf6aecc..481f9f400 100755
--- a/youtube-dl
+++ b/youtube-dl
@@ -693,7 +693,7 @@ class YoutubeIE(InfoExtractor):
 		'18': 'mp4',
 		'22': 'mp4',
 		'37': 'mp4',
-		'38': 'video',
+		'38': 'video', # You actually don't know if this will be MOV, AVI or whatever
 		'43': 'webm',
 		'45': 'webm',
 	}