diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index 13959f8b3d..328109b354 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -4210,7 +4210,7 @@ static int matroska_parse_cluster(MatroskaDemuxContext *matroska)
     MatroskaBlock     *block = &cluster->block;
     int res;
 
-    av_assert0(matroska->num_levels <= 2);
+    av_assert0(matroska->num_levels <= 2U);
 
     if (matroska->num_levels == 1) {
         res = ebml_parse(matroska, matroska_segment, NULL);