diff --git a/setup.py b/setup.py
index <HASH>..<HASH> 100644
--- a/setup.py
+++ b/setup.py
@@ -85,7 +85,7 @@ setup(
     # your project is installed. For an analysis of "install_requires" vs pip's
     # requirements files see:
     # https://packaging.python.org/en/latest/requirements.html
-    install_requires=['requests', 'envparse', 'typing', 'jsonschema'],
+    install_requires=['requests', 'envparse', 'typing', 'six', 'jsonschema'],
 
     setup_requires=['pytest-runner'],
     tests_require=['pytest', 'pytz', 'betamax', 'six'],
adding six to the setup

see also #<I>