diff --git a/libavformat/wtvdec.c b/libavformat/wtvdec.c
index 4dfe7010d1..48f51ad913 100644
--- a/libavformat/wtvdec.c
+++ b/libavformat/wtvdec.c
@@ -205,7 +205,7 @@ static AVIOContext * wtvfile_open_sector(int first_sector, uint64_t length, int
         return NULL;
     }
 
-    if ((int64_t)wf->sectors[wf->nb_sectors - 1] << WTV_SECTOR_BITS > avio_tell(s->pb))
+    if ((int64_t)wf->sectors[wf->nb_sectors - 1] << WTV_SECTOR_BITS > avio_size(s->pb))
         av_log(s, AV_LOG_WARNING, "truncated file\n");
 
     /* check length */