diff --git a/.travis.yml b/.travis.yml
index 250dbae..9e86ad1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,11 +1,18 @@
 language: python
-env:
-  - TOXENV=flake8
-  - TOXENV=py27
-  - TOXENV=py34
-  - TOXENV=py35
-  - TOXENV=py36
-  - TOXENV=pypy
+matrix:
+  include:
+    - python: 3.6
+      env: TOXENV=flake8
+    - python: 2.7
+      env: TOXENV=py27
+    - python: 3.4
+      env: TOXENV=py34
+    - python: 3.5
+      env: TOXENV=py35
+    - python: 3.6
+      env: TOXENV=py36
+    - python: pypy
+      env: TOXENV=pypy
 install:
   - pip install tox 
 script:
diff --git a/flask_moment.py b/flask_moment.py
index 7bfded1..089c5fb 100644
--- a/flask_moment.py
+++ b/flask_moment.py
@@ -48,11 +48,14 @@ def include_jquery(version='2.1.0', local_js=None):
     @staticmethod
     def locale(language='en', auto_detect=False):
         if auto_detect:
-            return Markup('<script>\nvar locale = window.navigator.userLanguage || window.navigator.language;\n'
+            return Markup('<script>\nvar locale = '
+                          'window.navigator.userLanguage || '
+                          'window.navigator.language;\n'
                           'moment.locale(locale);\n</script>')
         else:
-            return Markup('<script>\nmoment.locale("%s");\n</script>' % language)
-        
+            return Markup(
+                '<script>\nmoment.locale("%s");\n</script>' % language)
+
     @staticmethod
     def lang(language):
         return _moment.locale(language)
diff --git a/tests/test_flask_moment.py b/tests/test_flask_moment.py
index 37c70ec..3e3ae43 100644
--- a/tests/test_flask_moment.py
+++ b/tests/test_flask_moment.py
@@ -112,17 +112,15 @@ def test__moment_local_true(self):
 
     def test_locale(self):
         mom = _moment_mock()
-        l = 'en'
-        locale = mom.locale(l)
+        locale = mom.locale('en')
         assert isinstance(locale, Markup)
-        assert 'moment.locale("%s")' % l in str(locale)
+        assert 'moment.locale("en")' in str(locale)
 
     def test_lang(self):
         mom = _moment_mock()
-        l = 'en'
-        lang = mom.lang(l)
+        lang = mom.lang('en')
         assert isinstance(lang, Markup)
-        assert 'moment.locale("%s")' % l in str(lang)
+        assert 'moment.locale("en")' in str(lang)
 
     def test__moment_timestamp_passed(self):
         ts = datetime(2017, 1, 15, 22, 47, 6, 479898)
diff --git a/tox.ini b/tox.ini
index 1aef3bf..f68b1ec 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,6 +8,12 @@ deps=
     pytest
     pytest-cov
     mock
+basepython=
+    py27: python2.7
+    py34: python3.4
+    py35: python3.5
+    py36: python3.6
+    pypy: pypy
 
 [testenv:flake8]
 basepython=python3.6