diff --git a/tox.ini b/tox.ini
index 08ce8fa5..e2b735fb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,6 +4,7 @@ envlist = django{18,111}
 
 [testenv]
 usedevelop = True
+basepython = python2
 setenv =
   WCSCTL=wcs/wcsctl.py
   DJANGO_SETTINGS_MODULE=combo.settings