diff --git a/tox.ini b/tox.ini
index 029be5a..0447e70 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,7 +3,6 @@ minversion = 2.0
 envlist = py35,py27,pep8
 
 [testenv]
-basepython = python3
 install_command = pip install {opts} {packages}
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
@@ -18,6 +17,7 @@ commands =
 basepython = python2.7
 
 [testenv:pep8]
+basepython = python3
 deps =
   -r{toxinidir}/test-requirements.txt
 commands =
@@ -26,12 +26,15 @@ commands =
   bandit -r oslo_concurrency -x tests -n5 --skip B311,B404,B603,B606
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:docs]
+basepython = python3
 commands = python setup.py build_sphinx
 
 [testenv:cover]
+basepython = python3
 commands = python setup.py test --coverage --coverage-package-name=oslo_concurrency --testr-args='{posargs}'
 
 [flake8]
@@ -44,9 +47,11 @@ import_exceptions =
   oslo_concurrency._i18n
 
 [testenv:releasenotes]
+basepython = python3
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:lower-constraints]
+basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt