diff --git a/requirements.txt b/requirements.txt
index f3f606a..4c97b71 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,4 +8,4 @@ pyflakes==0.8.1
 flake8==2.2.4
 mccabe==0.2.1 # MIT License
 
-six>=1.7.0
+six>=1.9.0