diff --git a/setup.py b/setup.py
index c519a2c..2eb9117 100644
--- a/setup.py
+++ b/setup.py
@@ -21,4 +21,5 @@ def readme():
     entry_points={
         'console_scripts': ['flatten_json=flatten_json:cli']
     },
+    install_requires=['six'],
 )