diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 20dcecc7d2..b33fc2422a 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -1690,7 +1690,7 @@ AVOutputFormat mp4_muxer = {
     "mp4",
     NULL_IF_CONFIG_SMALL("MP4 format"),
     "application/mp4",
-    "mp4,m4a",
+    "mp4",
     sizeof(MOVContext),
     CODEC_ID_AAC,
     CODEC_ID_MPEG4,
@@ -1738,7 +1738,7 @@ AVOutputFormat ipod_muxer = {
     "ipod",
     NULL_IF_CONFIG_SMALL("iPod H.264 MP4 format"),
     "application/mp4",
-    NULL,
+    "m4v,m4a",
     sizeof(MOVContext),
     CODEC_ID_AAC,
     CODEC_ID_H264,