diff --git a/requirements.txt b/requirements.txt
index 144998ad8..c7ac2cf98 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -14,7 +14,7 @@ oslo.utils>=1.2.0                       # Apache-2.0
 pecan>=0.8.0
 psutil>=1.1.1,<2.0.0
 requests>=2.2.0,!=2.4.0
-six>=1.7.0
+six>=1.9.0
 stevedore>=1.1.0  # Apache-2.0
 WSME>=0.6
 oslotest>=1.2.0  # Apache-2.0