diff --git a/lib/matplotlib/collections.py b/lib/matplotlib/collections.py
index f660fd1eb67b..ad660e97ecbd 100644
--- a/lib/matplotlib/collections.py
+++ b/lib/matplotlib/collections.py
@@ -11,6 +11,8 @@
 from __future__ import (absolute_import, division, print_function,
                         unicode_literals)
 
+import warnings
+
 import six
 from six.moves import zip
 try: