diff --git a/libavformat/mov.c b/libavformat/mov.c
index dcec74662d..f0b4edc2ed 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -5095,7 +5095,7 @@ static int mov_read_sidx(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     // See if the remaining bytes are just an mfra which we can ignore.
     is_complete = offset == stream_size;
     if (!is_complete) {
-        int ret;
+        int64_t ret;
         int64_t original_pos = avio_tell(pb);
         int32_t mfra_size;
         if ((ret = avio_seek(pb, stream_size - 4, SEEK_SET)) < 0)