diff --git a/tox.ini b/tox.ini
index 63c27bbb..57b240cb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -49,6 +49,7 @@ setenv = OS_TEST_PATH=panko/tests/functional/
 commands = pifpaf run elasticsearch {toxinidir}/tools/pretty_tox.sh "{posargs}"
 
 [testenv:py35-elastic]
+basepython = python3
 setenv = OS_TEST_PATH=panko/tests/functional/
 commands = pifpaf run elasticsearch {toxinidir}/tools/pretty_tox.sh "{posargs}"
 
@@ -57,55 +58,68 @@ commands = pifpaf run elasticsearch {toxinidir}/tools/pretty_tox.sh "{posargs}"
 # gabbi tests without needing to do discovery across the entire body of
 # tests.
 [testenv:gabbi]
+basepython = python3
 setenv = OS_TEST_PATH=panko/tests/functional/gabbi
 passenv = PANKO_*
 commands = pifpaf run mongodb {toxinidir}/tools/pretty_tox.sh "{posargs}"
 
 [testenv:cover]
+basepython = python3
 setenv = OS_TEST_PATH=panko/tests
 commands =
    python setup.py testr --slowest --coverage --testr-args="{posargs}"
    coverage report
 
 [testenv:pep8]
+basepython = python3
 deps = hacking<0.13,>=0.12.0
        doc8
 commands = flake8
            doc8 {posargs}
 
 [testenv:releasenotes]
+basepython = python3
 commands = sphinx-build -a -E -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:genconfig]
+basepython = python3
 commands = oslo-config-generator --config-file=etc/panko/panko-config-generator.conf
 
 [testenv:genpolicy]
+basepython = python3
 commands = oslopolicy-sample-generator --config-file=etc/panko/panko-policy-generator.conf
 
 [testenv:docs]
+basepython = python3
 commands = python setup.py build_sphinx
 setenv = PYTHONHASHSEED=0
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 setenv = PYTHONHASHSEED=0
 
 [testenv:debug]
+basepython = python3
 commands = bash -x oslo_debug_helper {posargs}
 
 [testenv:debug-mongodb]
+basepython = python3
 setenv = OS_TEST_PATH=panko/tests/functional
 commands = pifpaf --debug run mongodb oslo_debug_helper {posargs}
 
 [testenv:debug-mysql]
+basepython = python3
 setenv = OS_TEST_PATH=panko/tests/functional
 commands = pifpaf --debug run mysql oslo_debug_helper {posargs}
 
 [testenv:debug-pgsql]
+basepython = python3
 setenv = OS_TEST_PATH=panko/tests/functional
 commands = pifpaf --debug run postgresql oslo_debug_helper {posargs}
 
 [testenv:debug-elastic]
+basepython = python3
 setenv = OS_TEST_PATH=panko/tests/functional
 commands = pifpaf --debug run elasticsearch oslo_debug_helper {posargs}