diff --git a/libmpdemux/asfheader.c b/libmpdemux/asfheader.c
index 4f9b8b8342..ac46ad888b 100644
--- a/libmpdemux/asfheader.c
+++ b/libmpdemux/asfheader.c
@@ -588,7 +588,7 @@ int read_asf_header(demuxer_t *demuxer,struct asf_priv* asf){
       asf->packetsize=fileh->max_packet_size;
       asf->packet=malloc(asf->packetsize); // !!!
       asf->packetrate=fileh->max_bitrate/8.0/(double)asf->packetsize;
-      asf->movielength=fileh->send_duration/10000000LL;
+      asf->movielength=(fileh->play_duration-fileh->preroll)/10000000LL;
   }
 
   // find content header