diff --git a/beetsplug/lastgenre/__init__.py b/beetsplug/lastgenre/__init__.py
index 2756f452c0..4374310ba3 100644
--- a/beetsplug/lastgenre/__init__.py
+++ b/beetsplug/lastgenre/__init__.py
@@ -174,6 +174,7 @@ def _sort_by_depth(self, tags):
         genre tree.
         """
         depth_tag_pairs = [(self._get_depth(t), t) for t in tags]
+        depth_tag_pairs = [e for e in depth_tag_pairs if e[0] is not None]
         depth_tag_pairs.sort(reverse=True)
         return [p[1] for p in depth_tag_pairs]
 
diff --git a/test/test_lastgenre.py b/test/test_lastgenre.py
index f57471f1cf..a70c65ca10 100644
--- a/test/test_lastgenre.py
+++ b/test/test_lastgenre.py
@@ -213,6 +213,18 @@ def mock_fetch_artist_genre(self, obj):
         self.assertEqual(res, (config['lastgenre']['fallback'].get(),
                          u'fallback'))
 
+    def test_sort_by_depth(self):
+        self._setup_config(canonical=True)
+        # Normal case.
+        tags = ('electronic', 'ambient', 'post-rock', 'downtempo')
+        res = self.plugin._sort_by_depth(tags)
+        self.assertEqual(
+            res, ['post-rock', 'downtempo', 'ambient', 'electronic'])
+        # Non-canonical tag ('chillout') present.
+        tags = ('electronic', 'ambient', 'chillout')
+        res = self.plugin._sort_by_depth(tags)
+        self.assertEqual(res, ['ambient', 'electronic'])
+
 
 def suite():
     return unittest.TestLoader().loadTestsFromName(__name__)