diff --git a/requirements.txt b/requirements.txt
index 80ddb2b1df..ccd95e1204 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -39,7 +39,7 @@ PyYAML>=3.1.0
 qpid-python
 requests>=2.2.0,!=2.4.0
 Routes>=1.12.3,!=2.0
-six>=1.7.0
+six>=1.9.0
 SQLAlchemy>=0.9.7,<=0.9.99
 sqlalchemy-migrate>=0.9.1,!=0.9.2
 stevedore>=1.1.0  # Apache-2.0