diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
index 5cc8fabd7a..2c3b598d75 100644
--- a/libavcodec/mpeg4videodec.c
+++ b/libavcodec/mpeg4videodec.c
@@ -883,7 +883,7 @@ int ff_mpeg4_decode_partitions(Mpeg4DecContext *ctx)
     const int part_a_end   = s->pict_type == AV_PICTURE_TYPE_I ? (ER_DC_END   | ER_MV_END)   : ER_MV_END;
 
     mb_num = mpeg4_decode_partition_a(ctx);
-    if (mb_num < 0) {
+    if (mb_num <= 0) {
         ff_er_add_slice(&s->er, s->resync_mb_x, s->resync_mb_y,
                         s->mb_x, s->mb_y, part_a_error);
         return -1;