diff --git a/requirements-py2.txt b/requirements-py2.txt
index 083caec0..3f1f9729 100644
--- a/requirements-py2.txt
+++ b/requirements-py2.txt
@@ -11,7 +11,7 @@ pbr>=0.6,!=0.7,<1.0
 ordereddict
 
 # Python 2->3 compatibility library.
-six>=1.7.0
+six>=1.9.0
 
 # Very nice graph library
 networkx>=1.8
diff --git a/requirements-py3.txt b/requirements-py3.txt
index b04fc0af..6809a013 100644
--- a/requirements-py3.txt
+++ b/requirements-py3.txt
@@ -8,7 +8,7 @@ pbr>=0.6,!=0.7,<1.0
 # Packages needed for using this library.
 
 # Python 2->3 compatibility library.
-six>=1.7.0
+six>=1.9.0
 
 # Very nice graph library
 networkx>=1.8