diff --git a/requirements.txt b/requirements.txt
index 50f28a18..b2d752f3 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,3 +5,4 @@ PrettyTable>=0.7,<0.8
 python-keystoneclient>=0.9.0
 pyOpenSSL>=0.11
 warlock>=1.0.1,<2
+six>=1.7.0