diff --git a/libavformat/avidec.c b/libavformat/avidec.c
index 5abb9def3c..3e85d4e36e 100644
--- a/libavformat/avidec.c
+++ b/libavformat/avidec.c
@@ -1341,7 +1341,7 @@ static int guess_ni_flag(AVFormatContext *s){
     if (last_start > first_end)
         return 1;
     idx= av_mallocz(sizeof(*idx) * s->nb_streams);
-    for (min_pos=pos=0; min_pos!=INT64_MAX; pos= min_pos+1) {
+    for (min_pos=pos=0; min_pos!=INT64_MAX; pos= min_pos+1LU) {
         int64_t max_dts = INT64_MIN/2, min_dts= INT64_MAX/2;
         min_pos = INT64_MAX;