diff --git a/tox.ini b/tox.ini
index 30999fa..08685c7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,10 +3,10 @@ minversion = 2.0
 envlist = py35,py27,docs,pep8
 
 [testenv:docs]
+basepython = python3
 commands = python setup.py build_sphinx
 
 [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}
@@ -15,6 +15,7 @@ deps =
 commands = python setup.py test --slowest --testr-args='{posargs}'
 
 [testenv:pep8]
+basepython = python3
 commands = flake8 {posargs}
 
 [testenv:py27]
@@ -25,6 +26,7 @@ commands =
     doc8 --ignore-path "doc/source/history.rst" doc/source
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [flake8]
@@ -32,9 +34,11 @@ show-source = True
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build
 
 [testenv:cover]
+basepython = python3
 commands = python setup.py test --coverage --testr-args="{posargs}"
 
 [testenv:releasenotes]
+basepython = python3
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:lower-constraints]