diff --git a/tox.ini b/tox.ini
index bad7d67..91786a4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,7 +3,6 @@ minversion = 2.0
 envlist = py35,py27,pep8
 
 [testenv]
-basepython = python3
 setenv =
     VIRTUAL_ENV={envdir}
     BRANCH_NAME=master
@@ -16,6 +15,7 @@ deps =
 commands = python setup.py testr --slowest --testr-args='{posargs}'
 
 [testenv:debug]
+basepython = python3
 commands = oslo_debug_helper {posargs}
 
 [testenv:debug-py27]
@@ -23,15 +23,19 @@ basepython = python2.7
 commands = oslo_debug_helper {posargs}
 
 [testenv:pep8]
+basepython = python3
 commands = flake8
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:cover]
+basepython = python3
 commands = python setup.py testr --coverage --testr-args='{posargs}'
 
 [testenv:docs]
+basepython = python3
 commands = python setup.py build_sphinx
 
 [testenv:py27]
@@ -48,9 +52,11 @@ ignore = E123,E125
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build
 
 [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