diff --git a/tox.ini b/tox.ini
index 9b12f77..9ef6090 100644
--- a/tox.ini
+++ b/tox.ini
@@ -22,12 +22,15 @@ whitelist_externals =
   find
 
 [testenv:pep8]
+basepython = python3
 commands = flake8 {posargs}
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:cover]
+basepython = python3
 setenv =
     PYTHON=coverage run --source $project --parallel-mode
 commands =
@@ -37,13 +40,16 @@ commands =
     coverage xml -o cover/coverage.xml
 
 [testenv:docs]
+basepython = python3
 commands = python setup.py build_sphinx
 
 [testenv:releasenotes]
+basepython = python3
 commands =
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:debug]
+basepython = python3
 whitelist_externals = oslo_debug_helper
 commands = oslo_debug_helper -t mistral_lib/tests {posargs}