diff --git a/tox.ini b/tox.ini
index 52a3e39..35999c6 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,12 +13,15 @@ deps = -r{toxinidir}/requirements.txt
 commands = stestr run --slowest {posargs}
 
 [testenv:pep8]
+basepython = python3
 commands = flake8
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:cover]
+basepython = python3
 setenv =
     PYTHON=coverage run --source instack --parallel-mode
 commands =