diff --git a/tox.ini b/tox.ini
index e4bcf854..318a363a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py26,py27,pep8
+envlist = py26,py27,py33,pep8
 
 [testenv]
 setenv = VIRTUAL_ENV={envdir}