diff --git a/03_classification.ipynb b/03_classification.ipynb
index 01207f4..444f52f 100644
--- a/03_classification.ipynb
+++ b/03_classification.ipynb
@@ -1053,7 +1053,7 @@
     "    \"\"\"If you prefer color and a colorbar\"\"\"\n",
     "    fig = plt.figure(figsize=(8,8))\n",
     "    ax = fig.add_subplot(111)\n",
-    "    cax = ax.matshow(conf_mx)\n",
+    "    cax = ax.matshow(matrix)\n",
     "    fig.colorbar(cax)"
    ]
   },