diff --git a/beets/ui/commands.py b/beets/ui/commands.py
index 610ae551e..46ae1d936 100644
--- a/beets/ui/commands.py
+++ b/beets/ui/commands.py
@@ -237,7 +237,7 @@ def show_change(cur_artist, cur_album, match):
             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)
diff --git a/beetsplug/keyfinder.py b/beetsplug/keyfinder.py
index 34a4abca4..a3fbc8211 100644
--- a/beetsplug/keyfinder.py
+++ b/beetsplug/keyfinder.py
@@ -48,7 +48,7 @@ class KeyFinderPlugin(BeetsPlugin):
         self.find_key(lib.items(ui.decargs(args)), write=ui.should_write())
 
     def imported(self, session, task):
-        self.find_key(task.items)
+        self.find_key(task.imported_items())
 
     def find_key(self, items, write=False):
         overwrite = self.config['overwrite'].get(bool)
diff --git a/docs/changelog.rst b/docs/changelog.rst
index ec6c1b3a7..8b49b97a1 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -106,6 +106,8 @@ Fixes:
 * The importer now supports audio files contained in data tracks when they are
   listed in MusicBrainz: the corresponding audio tracks are now merged into the
   main track list. Thanks to :user:`jdetrey`. :bug:`1638`
+* :doc:`/plugins/keyfinder`: Avoid a crash when trying to process unmatched
+  tracks. :bug:`2537`
 
 
 For developers: