diff --git a/.gitignore b/.gitignore
index 041e191..f261714 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,3 +15,4 @@ ChangeLog
 # Editors
 *~
 .*.swp
+/.testrepository
diff --git a/tox.ini b/tox.ini
index 22c2faa..a030331 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,7 +1,9 @@
 [tox]
 minversion = 1.6
 skipdist = True
-envlist = pep8, py27, pypy, py33, py34
+skip_missing_interpreters = true
+# https://docs.python.org/devguide/#status-of-python-branches
+envlist = pep8, py27, pypy, py33, py34, py35, py36, py37
 
 [testenv]
 commands = python setup.py test --slowest --testr-args='{posargs}'