diff --git a/tox.ini b/tox.ini
index bf733a3..0a3a0e2 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,6 +4,7 @@
 skipsdist = True
 
 [testenv]
+basepython = python3
 usedevelop = True
 install_command = pip install {opts} {packages}
 setenv =
@@ -14,6 +15,9 @@
        -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands = python setup.py testr --slowest --testr-args='{posargs}'
+
+[testenv:py27]
+basepython = python2.7
 
 [testenv:pep8]
 commands =
@@ -83,7 +87,6 @@
 import_exceptions = castellan.i18n
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt