diff --git a/libavformat/mov.c b/libavformat/mov.c
index 8af564ed61..4e3eed579e 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -7637,10 +7637,11 @@ static int mov_read_iloc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         return 0;
     }
 
-    if (c->fc->nb_streams) {
+    if (c->avif_info) {
         av_log(c->fc, AV_LOG_INFO, "Duplicate iloc box found\n");
         return 0;
     }
+    av_assert0(!c->fc->nb_streams);
 
     version = avio_r8(pb);
     avio_rb24(pb);  // flags.