diff --git a/deep_sort/tracker.py b/deep_sort/tracker.py
index de99de44..e7701155 100644
--- a/deep_sort/tracker.py
+++ b/deep_sort/tracker.py
@@ -103,10 +103,10 @@ def gated_metric(tracks, dets, track_indices, detection_indices):
             return cost_matrix
 
         # Split track set into confirmed and unconfirmed tracks.
-        confirmed_tracks = [
-            i for i, t in enumerate(self.tracks) if t.is_confirmed()]
-        unconfirmed_tracks = [
-            i for i, t in enumerate(self.tracks) if not t.is_confirmed()]
+        confirmed_tracks = list()
+        unconfirmed_tracks = list()
+        for i, t in enumerate(self.tracks):
+            confirmed_tracks.append(i) if t.is_confirmed() else unconfirmed_tracks.append(i)
 
         # Associate confirmed tracks using appearance features.
         matches_a, unmatched_tracks_a, unmatched_detections = \