diff --git a/libavformat/concatdec.c b/libavformat/concatdec.c
index 73f8a63a2b..e57e5ce0ec 100644
--- a/libavformat/concatdec.c
+++ b/libavformat/concatdec.c
@@ -324,7 +324,7 @@ static int open_file(AVFormatContext *avf, unsigned fileno)
     if (!cat->avf)
         return AVERROR(ENOMEM);
 
-    cat->avf->flags |= avf->flags;
+    cat->avf->flags |= avf->flags & ~AVFMT_FLAG_CUSTOM_IO;
     cat->avf->interrupt_callback = avf->interrupt_callback;
 
     if ((ret = ff_copy_whiteblacklists(cat->avf, avf)) < 0)