diff --git a/tox.ini b/tox.ini
index e647c7c130..4b47d9e049 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,6 +9,7 @@ install_command = pip install -U {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/test-requirements.txt
 whitelist_externals = bash
+basepython = python2
 
 [testenv:releasenotes]
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html