Index: libmpdemux/demux_mkv.c
===================================================================
--- libmpdemux/demux_mkv.c	(revisione 28704)
+++ libmpdemux/demux_mkv.c	(copia locale)
@@ -2928,7 +2928,7 @@
       if (target_timecode < 0)
         target_timecode = 0;
 
-      if (mkv_d->indexes == NULL)  /* no index was found */
+      if (mkv_d->indexes == NULL & mkv_d->num_cluster_pos > 0)  /* no index was found */
         {
           uint64_t target_filepos, cluster_pos, max_pos;
 
@@ -2984,7 +2984,8 @@
               stream_seek (s, cluster_pos);
             }
         }
-      else
+
+      if (mkv_d->indexes)
         {
           mkv_index_t *index = NULL;
           int seek_id = (demuxer->video->id < 0) ? demuxer->audio->id : demuxer->video->id;