diff --git a/libavformat/mm.c b/libavformat/mm.c
index 91d22d09d8..d7308b9a90 100644
--- a/libavformat/mm.c
+++ b/libavformat/mm.c
@@ -174,7 +174,6 @@ static int read_packet(AVFormatContext *s,
         case MM_TYPE_AUDIO :
             if (av_get_packet(s->pb, pkt, length)<0)
                 return AVERROR(ENOMEM);
-            pkt->size = length;
             pkt->stream_index = 1;
             pkt->pts = mm->audio_pts++;
             return 0;