diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 00818b54fb..d096f7204b 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -149,7 +149,8 @@ static void put_ebml_num(ByteIOContext *pb, uint64_t num, int bytes)
 static void put_ebml_uint(ByteIOContext *pb, unsigned int elementid, uint64_t val)
 {
     int i, bytes = 1;
-    while (bytes < 8 && val >> bytes*8) bytes++;
+    uint64_t tmp = val;
+    while (tmp>>=8) bytes++;
 
     put_ebml_id(pb, elementid);
     put_ebml_num(pb, bytes, 0);