diff --git a/setup.py b/setup.py
index 40dbc0f..eb5f5f6 100644
--- a/setup.py
+++ b/setup.py
@@ -60,6 +60,7 @@
 install_requires = [
     'httplib2>=0.8',
     'oauth2client>=1.3',
+    'six>=1.6.1',
     'uritemplate>=0.6',
 ]