diff --git a/18_reinforcement_learning.ipynb b/18_reinforcement_learning.ipynb
index 5633d2e..9ad70dc 100644
--- a/18_reinforcement_learning.ipynb
+++ b/18_reinforcement_learning.ipynb
@@ -1450,7 +1450,7 @@
     "\n",
     "class ReplayBuffer:\n",
     "    def __init__(self, max_size):\n",
-    "        self.buffer = np.empty(max_size, dtype=np.object)\n",
+    "        self.buffer = np.empty(max_size, dtype=object)\n",
     "        self.max_size = max_size\n",
     "        self.index = 0\n",
     "        self.size = 0\n",