diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index cd93f45..fc40c72 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -247,7 +247,7 @@ static unsigned int descrLength(unsigned int len)
 
 static void putDescr(AVIOContext *pb, int tag, unsigned int size)
 {
-    int i= descrLength(size) - size - 2;
+    int i= 3;
     avio_w8(pb, tag);
     for(; i>0; i--)
         avio_w8(pb, (size>>(7*i)) | 0x80);
