diff --git a/requirements.txt b/requirements.txt
index 2aa3fc45f..f70be2ece 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,7 +8,7 @@ requests>=2.2.0,!=2.4.0
 netaddr>=0.7.12
 SQLAlchemy>=0.9.7,<=0.9.99
 alembic>=0.7.2
-six>=1.7.0
+six>=1.9.0
 oslo.config>=1.6.0  # Apache-2.0
 oslo.db>=1.4.1  # Apache-2.0
 oslo.messaging>=1.6.0