diff --git a/tutorials/W3D4_ReinforcementLearning/W3D4_Tutorial1.ipynb b/tutorials/W3D4_ReinforcementLearning/W3D4_Tutorial1.ipynb
index 89ab1d2c23..e46a4dca70 100644
--- a/tutorials/W3D4_ReinforcementLearning/W3D4_Tutorial1.ipynb
+++ b/tutorials/W3D4_ReinforcementLearning/W3D4_Tutorial1.ipynb
@@ -185,8 +185,8 @@
     "  if not ax:\n",
     "    fig, ax = plt.subplots()\n",
     "\n",
-    "  indx = np.arange(0, TDE.shape[1], skip)\n",
-    "  im = ax.imshow(TDE[:,indx])\n",
+    "  index = np.arange(0, TDE.shape[1], skip)\n",
+    "  im = ax.imshow(TDE[:,index])\n",
     "  positions = ax.get_xticks()\n",
     "  # Avoid warning when setting string tick labels\n",
     "  ax.xaxis.set_major_locator(ticker.FixedLocator(positions))\n",