diff --git a/18_reinforcement_learning.ipynb b/18_reinforcement_learning.ipynb
index 4d36515..5e188d1 100644
--- a/18_reinforcement_learning.ipynb
+++ b/18_reinforcement_learning.ipynb
@@ -52,7 +52,8 @@
     "\n",
     "if IS_COLAB or IS_KAGGLE:\n",
     "    !apt update && apt install -y libpq-dev libsdl2-dev swig xorg-dev xvfb\n",
-    "    !pip install -q -U tf-agents pyvirtualdisplay gym[atari,box2d]\n",
+    "    !pip install -q -U tf-agents pyvirtualdisplay gym[box2d]\n",
+    "    !pip install -q -U atari_py==0.2.5\n",
     "\n",
     "# Scikit-Learn ≥0.20 is required\n",
     "import sklearn\n",
diff --git a/requirements.txt b/requirements.txt
index 767ded9..0b7d84d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -49,7 +49,9 @@ tensorflow-addons==0.12.1
 
 # There are a few dependencies you need to install first, check out:
 # https://github.com/openai/gym#installing-everything
-gym[atari,Box2D]==0.18.0
+gym[Box2D]==0.18.0
+atari_py==0.2.5
+
 # On Windows, install atari_py using:
 # pip install --no-index -f https://github.com/Kojoley/atari-py/releases atari_py