diff --git a/tox.ini b/tox.ini
index 55e573d..b93092c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -17,9 +17,11 @@ commands =
     stestr run --slowest {posargs}
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:docs]
+basepython = python3
 setenv = PYTHONHASHSEED=0
 commands =
     find . -type f -name "*.pyc" -delete
@@ -27,6 +29,7 @@ commands =
     python setup.py build_sphinx
 
 [testenv:pep8]
+basepython = python3
 deps = -r{toxinidir}/test-requirements.txt
 commands =
     doc8 doc/source/ README.rst