diff --git a/setup.py b/setup.py
index 8f12da64..8f6f88be 100644
--- a/setup.py
+++ b/setup.py
@@ -62,7 +62,8 @@ install_requires = [
     'acme==0.13.0',
     'retrying==1.3.3',
     'tabulate==0.7.7',
-    'pem==16.1.0'
+    'pem==16.1.0',
+    'pyOpenSSL==17.0.0'
 ]
 
 tests_require = [