diff --git a/libavformat/mov.c b/libavformat/mov.c
index 4550abd25c..8771a8d6b7 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -4396,7 +4396,7 @@ static int mov_read_keys(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
 static int mov_read_custom(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 {
-    int64_t end = avio_tell(pb) + atom.size;
+    int64_t end = av_sat_add64(avio_tell(pb), atom.size);
     uint8_t *key = NULL, *val = NULL, *mean = NULL;
     int i;
     int ret = 0;