diff --git a/setup.py b/setup.py
index 90ab546..8739cae 100644
--- a/setup.py
+++ b/setup.py
@@ -31,7 +31,7 @@
             'test/pki/ca/*.0'
             ],
     },
-    install_requires=['PyOpenSSL', 'pyasn1>=0.1.1'],
+    install_requires=['PyOpenSSL', 'pyasn1>=0.1.1', 'setuptools>=3.5'],
     python_requires='>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*',
     classifiers=[
         'Development Status :: 5 - Production/Stable',