diff --git a/setup.py b/setup.py
index 3933b2b..cd8580c 100755
--- a/setup.py
+++ b/setup.py
@@ -47,11 +47,15 @@ def get_version():
     ],
     extras_require={
         'dev': [
-            'mock==2.0.0; python_version < "3.3"',
-            'mypy==0.501; python_version >= "3.3"',
             'pycodestyle==2.3.1',
             'pytest==3.0.6',
             'pytest-randomly==1.1.2',
+        ],
+        'dev: python_version < "3.3"': [
+            'mock==2.0.0',
+        ],
+        'dev: python_version >= "3.3"': [
+            'mypy==0.501',
         ]
     }
 )