diff --git a/tox.ini b/tox.ini
index de47800..ecaae55 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,6 +3,7 @@ envlist = py26,py27,py32,py33,py34,py35
 
 [testenv]
 deps =
+    mock
     pytest
 commands =
     py.test