diff --git a/lib/matplotlib/backend_tools.py b/lib/matplotlib/backend_tools.py
index 0b00995241b8..899eee475594 100644
--- a/lib/matplotlib/backend_tools.py
+++ b/lib/matplotlib/backend_tools.py
@@ -18,6 +18,7 @@
 from weakref import WeakKeyDictionary
 import numpy as np
 from matplotlib.externals import six
+import warnings
 
 
 class Cursors(object):