diff --git a/libavcodec/mmvideo.c b/libavcodec/mmvideo.c
index 21d6669327..b480533128 100644
--- a/libavcodec/mmvideo.c
+++ b/libavcodec/mmvideo.c
@@ -114,7 +114,7 @@ static int mm_decode_intra(MmContext * s, int half_horiz, int half_vert)
 
         if (color) {
             memset(s->frame.data[0] + y*s->frame.linesize[0] + x, color, run_length);
-            if (half_vert)
+            if (half_vert && y + half_vert < s->avctx->height)
                 memset(s->frame.data[0] + (y+1)*s->frame.linesize[0] + x, color, run_length);
         }
         x+= run_length;