diff --git a/tox.ini b/tox.ini
index 200c3c1b7..94f2f1348 100644
--- a/tox.ini
+++ b/tox.ini
@@ -47,6 +47,7 @@ commands =
 
 #set PYTHONHASHSEED=0 to prevent wsmeext.sphinxext from randomly failing.
 [testenv:venv]
+basepython = python2.7
 setenv = PYTHONHASHSEED=0
 commands = {posargs}