diff --git a/tox.ini b/tox.ini
index dd39c783..cc20e85d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -25,6 +25,7 @@ commands =
   pip install -e ../horizon
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:pep8]