diff --git a/tox.ini b/tox.ini
index 3c55969..883c9fb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,6 +3,7 @@ minversion = 2.0
 envlist = py35,py27,pypy,pep8
 
 [testenv]
+basepython = python3
 install_command = pip install {opts} {packages}
 whitelist_externals =
  /bin/sh
@@ -12,6 +13,9 @@ deps =
   -r{toxinidir}/requirements.txt
 commands = python setup.py testr --slowest --testr-args='{posargs}'
 
+[testenv:py27]
+basepython = python2.7
+
 [testenv:pep8]
 deps =
   -r{toxinidir}/test-requirements.txt
@@ -48,7 +52,6 @@ import_exceptions =
 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