diff --git a/tox.ini b/tox.ini
index 2eb1f8a..9d156dd 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py26, py27
+envlist = py26, py27, py33
 
 [testenv]
 deps = -r{toxinidir}/requirements.pip