diff --git a/tox.ini b/tox.ini
index dcdd8b546a..67bb3b173e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -27,6 +27,7 @@ commands =
   stestr run '^(?!heat_integrationtests){posargs}'
 
 [testenv:pep8]
+basepython = python3
 commands =
     flake8 heat bin/heat-api bin/heat-api-cfn bin/heat-engine bin/heat-manage contrib heat_integrationtests doc/source
     python tools/custom_guidelines.py --exclude heat/engine/resources/aws
@@ -46,9 +47,11 @@ commands =
     bandit -r heat -x tests --skip B101,B104,B107,B110,B310,B311,B404,B410,B504,B506,B603,B607
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:cover]
+basepython = python3
 setenv =
   PYTHON=coverage run --source heat --parallel-mode
 commands =
@@ -61,12 +64,14 @@ commands =
   coverage report
 
 [testenv:docs]
+basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands =
   rm -rf doc/build
   sphinx-build -b html doc/source doc/build/html
 
 [testenv:api-ref]
+basepython = python3
 # This environment is called from CI scripts to test and publish
 # the API Ref to developer.openstack.org.
 deps = -r{toxinidir}/doc/requirements.txt
@@ -77,15 +82,18 @@ commands =
   sphinx-build -W -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
 
 [testenv:genconfig]
+basepython = python3
 commands =
     oslo-config-generator --config-file=config-generator.conf
     oslo-config-generator --config-file=heat_integrationtests/config-generator.conf
 
 [testenv:genpolicy]
+basepython = python3
 commands =
     oslopolicy-sample-generator --config-file etc/heat/heat-policy-generator.conf
 
 [testenv:bandit]
+basepython = python3
 deps = -r{toxinidir}/test-requirements.txt
 # The following bandit tests are being skipped:
 # B101: Test for use of assert
@@ -112,9 +120,11 @@ import_exceptions = heat.common.i18n
 local-check-factory = heat.hacking.checks.factory
 
 [testenv:debug]
+basepython = python3
 commands = oslo_debug_helper {posargs}
 
 [testenv:releasenotes]
+basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html