diff --git a/setup.py b/setup.py
index 69ea451f58c2d62e117fc961982650560ca326db..0c19b0f7e4bc4e5286b0ad1b705f466bacfc0b0d 100644
--- a/setup.py
+++ b/setup.py
@@ -212,6 +212,7 @@ def main():
                 "decorator>=3.2.0",
                 "cffi>=1.1.0",
                 "appdirs>=1.4.0",
+                "six>=1.9.0",
                 # "Mako>=0.3.6",
                 ],