diff --git a/tests/events/test_events.py b/tests/events/test_events.py
index e7c6ca8e..40bf0c2f 100644
--- a/tests/events/test_events.py
+++ b/tests/events/test_events.py
@@ -21,6 +21,7 @@ from nose_parameterized import parameterized
 import pandas as pd
 from six import iteritems
 from six.moves import range, map
+from toolz import concat
 
 import zipline.utils.events
 from zipline.utils.calendars import get_calendar