diff --git a/requirements.txt b/requirements.txt
index b5b8bb631..0a0d5e9a6 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -47,7 +47,7 @@ pyzmail>=1.0.3
 requests!=2.12.*
 rfc2html>=2.0.0
 selenium>=2.42,<3.8.1
-six>=1.8.0
+six>=1.9.0
 sqlparse>=0.2.2
 tblib>=1.3.0
 tqdm>=3.7.0