diff --git a/scripts/marathon-health-check-testing/HealthCheckBencher.py b/scripts/marathon-health-check-testing/HealthCheckBencher.py
index 3fabe4d..daf8245 100755
--- a/scripts/marathon-health-check-testing/HealthCheckBencher.py
+++ b/scripts/marathon-health-check-testing/HealthCheckBencher.py
@@ -13,6 +13,7 @@ from marathon.models import MarathonHealthCheck
 from Queue import Empty
 from Queue import Queue
 from random import random
+import six
 from threading import Thread
 from time import sleep
 from urllib2 import urlopen
@@ -198,7 +199,7 @@ class HealthCheckBencher(object):
     def start_test(self):
         task_list = self.get_tasks()
         for action in self.action_list:
-            if isinstance(action, basestring):
+            if isinstance(action, six.text_type):
                 if action.startswith('sleep='):
                     amount = int(action.split('=')[1])
                     sleep(60*amount)
diff --git a/tox.ini b/tox.ini
index 189de06..3a3fecb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,7 +5,6 @@ skipsdist = True
 
 [testenv]
 usedevelop = True
-basepython = python2.7
 # --ignore-installed is added to workaround problem with pip 8.0 and argparse
 # https://github.com/pypa/pip/issues/3404 and
 # https://github.com/pypa/pip/issues/3384
@@ -21,12 +20,15 @@ commands =
   python setup.py test --slowest --testr-args='{posargs}'
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:pep8]
+basepython = python3
 commands = flake8
 
 [testenv:docs]
+basepython = python3
 commands =
     python setup.py build_sphinx