diff --git a/setup.py b/setup.py
index 8ef5b3c87a110b21de30b47a3f0a9ed4f721d942..93acd7ea515b0744f9a3fd8232e5e7aad523c799 100644
--- a/setup.py
+++ b/setup.py
@@ -56,7 +56,7 @@ def main():
               "leap>=2015.1",
               "dagrt>=2015.1",
 
-              "six",
+              "six>=1.6",
               ])