diff --git a/setup.py b/setup.py
index a3252bf..f134ffe 100644
--- a/setup.py
+++ b/setup.py
@@ -16,7 +16,7 @@
           'tabulate',
           'argparse',
           'networkx',
-          'six',
+          'six>=1.9',
           'ryu',
           'oslo.config',
           'pytest'