diff --git a/beets/autotag/match.py b/beets/autotag/match.py
index db4a35b132..a7121fd347 100644
--- a/beets/autotag/match.py
+++ b/beets/autotag/match.py
@@ -127,15 +127,21 @@ def assign_items(
     objects. These "extra" objects occur when there is an unequal number
     of objects of the two types.
     """
+    log.debug("Computing track assignment...")
     # Construct the cost matrix.
     costs = [[float(track_distance(i, t)) for t in tracks] for i in items]
-    # Find a minimum-cost bipartite matching.
-    log.debug("Computing track assignment...")
-    cost, _, assigned_idxs = lap.lapjv(np.array(costs), extend_cost=True)
+    # Assign items to tracks
+    _, _, assigned_item_idxs = lap.lapjv(np.array(costs), extend_cost=True)
     log.debug("...done.")
 
-    # Produce the output matching.
-    mapping = {items[i]: tracks[t] for (t, i) in enumerate(assigned_idxs)}
+    # Each item in `assigned_item_idxs` list corresponds to a track in the
+    # `tracks` list. Each value is either an index into the assigned item in
+    # `items` list, or -1 if that track has no match.
+    mapping = {
+        items[iidx]: t
+        for iidx, t in zip(assigned_item_idxs, tracks)
+        if iidx != -1
+    }
     extra_items = list(set(items) - mapping.keys())
     extra_items.sort(key=lambda i: (i.disc, i.track, i.title))
     extra_tracks = list(set(tracks) - set(mapping.values()))
diff --git a/test/test_autotag.py b/test/test_autotag.py
index e131a6be17..d6f4606e16 100644
--- a/test/test_autotag.py
+++ b/test/test_autotag.py
@@ -551,7 +551,7 @@ def test_order_works_with_invalid_track_numbers(self):
     def test_order_works_with_missing_tracks(self):
         items = []
         items.append(self.item("one", 1))
-        items.append(self.item("three", 3))
+        items.append(self.item("two", 2))
         trackinfo = []
         trackinfo.append(TrackInfo(title="one"))
         trackinfo.append(TrackInfo(title="two"))
@@ -560,8 +560,8 @@ def test_order_works_with_missing_tracks(self):
             items, trackinfo
         )
         assert extra_items == []
-        assert extra_tracks == [trackinfo[1]]
-        assert mapping == {items[0]: trackinfo[0], items[1]: trackinfo[2]}
+        assert extra_tracks == [trackinfo[2]]
+        assert mapping == {items[0]: trackinfo[0], items[1]: trackinfo[1]}
 
     def test_order_works_with_extra_tracks(self):
         items = []