diff --git a/setup.py b/setup.py
index 623ddaee146c21e9aa9fe11aeaa4359dba7e46b3..9283edd584a9fcfac0ccf457410fb529ffeae0b5 100644
--- a/setup.py
+++ b/setup.py
@@ -46,7 +46,7 @@ setup(name="pytools",
       install_requires=[
           "decorator>=3.2.0",
           "appdirs>=1.4.0",
-          "six",
+          "six>=1.8.0",
           ],
 
       author="Andreas Kloeckner",