diff --git a/libavcodec/fmvc.c b/libavcodec/fmvc.c
index ff5f291da6..2368e95f29 100644
--- a/libavcodec/fmvc.c
+++ b/libavcodec/fmvc.c
@@ -459,7 +459,7 @@ static int decode_frame(AVCodecContext *avctx,
             int size, offset, start = 0;
 
             offset = bytestream2_get_le16(gb);
-            if (offset > s->nb_blocks)
+            if (offset >= s->nb_blocks)
                 return AVERROR_INVALIDDATA;
 
             size = bytestream2_get_le16(gb);