diff --git a/tox.ini b/tox.ini
index 83c5a8e..08f72aa 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py26, py27, py32, pypy
+envlist = py26, py27, py32, py33, pypy
 
 [testenv]
 commands = python setup.py test