diff --git a/requirements.txt b/requirements.txt
index 95692398..420d3da4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,7 +4,7 @@
 pbr>=0.6,!=0.7,<1.0
 argparse
 requests>=2.2.0,!=2.4.0
-six>=1.7.0
+six>=1.9.0
 python-keystoneclient>=1.1.0
 cliff>=1.7.0  # Apache-2.0
 oslo.i18n>=1.3.0  # Apache-2.0