diff --git a/setup.py b/setup.py
index 1f1ea68769f71663dc719d274dc38b01b1f602ed..c8c660666ffeed18f92e533b6042cff63988a096 100644
--- a/setup.py
+++ b/setup.py
@@ -41,7 +41,7 @@ setup(name="loo.py",
           "pymbolic>=2015.2.1",
           "cgen>=2013.1.2",
           "islpy>=2014.2",
-          "six",
+          "six>=1.8.0",
           ],
 
       scripts=["bin/loopy"],