diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index f9e69c6c89..c484d95c2f 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -183,7 +183,7 @@ typedef struct MatroskaMuxContext {
 
 static int ebml_id_size(uint32_t id)
 {
-    return (av_log2(id + 1) - 1) / 7 + 1;
+    return (av_log2(id) + 7U) / 8;
 }
 
 static void put_ebml_id(AVIOContext *pb, uint32_t id)