diff --git a/tox.ini b/tox.ini
index 69cd121ac1..6b2cfb5cbf 100644
--- a/tox.ini
+++ b/tox.ini
@@ -10,6 +10,7 @@ deps = -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/re
 passenv = *_proxy *_PROXY
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:docs]