diff --git a/doc/source/conf.py b/doc/source/conf.py
index 6699b82e..1d5cb109 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -17,6 +17,7 @@ from __future__ import unicode_literals
 import os
 import subprocess
 import sys
+import warnings
 
 import pbr.version