diff --git a/tox.ini b/tox.ini
index a4c52e4..22edcc5 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 minversion = 2.0
-envlist = py27,pypy,pep8
+envlist = py27,py35,pypy,pep8
 skipsdist = True
 
 [testenv]
@@ -44,6 +44,7 @@ commands =
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:debug]
+basepython = python3
 commands = oslo_debug_helper {posargs}
 
 [flake8]