diff --git a/beets/ui/commands.py b/beets/ui/commands.py
index 610ae551e3..46ae1d9369 100644
--- a/beets/ui/commands.py
+++ b/beets/ui/commands.py
@@ -237,7 +237,7 @@ def format_index(track_info):
             medium = track_info.disc
             mediums = track_info.disctotal
         if config['per_disc_numbering']:
-            if mediums > 1:
+            if mediums and mediums > 1:
                 return u'{0}-{1}'.format(medium, medium_index)
             else:
                 return six.text_type(medium_index or index)