Update setup.py
diff --git a/setup.py b/setup.py
index d2d708ceaf7..835cb60cb37 100644
--- a/setup.py
+++ b/setup.py
@@ -32,7 +32,7 @@
       zip_safe=False,
       install_requires=[
           'scipy', 'numpy>=1.10.4', 'six', 'pyglet>=1.2.0,<=1.3.2', 'cloudpickle~=1.2.0',
-          'enum34~=1.1.6;python_version<"3.4"'
+          'enum34~=1.1.6;python_version<"3.4"', 'opencv-python'
       ],
       extras_require=extras,
       package_data={'gym': [

Just added opencv-python to be installed as a requirement. The new atari_preprocessing.py wrapper needs it.