diff --git a/requirements.txt b/requirements.txt
index a9385ad..175a884 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,7 +2,7 @@ requests>=1.2
 keyring>=8.0,<9.0
 keyrings.alt>=1.0,<2.0
 click>=6.0,<7.0
-six
+six>=1.9.0
 tzlocal
 certifi
 bitstring