diff --git a/ch12/ch12.ipynb b/ch12/ch12.ipynb
index 45870f58..eefd3abc 100644
--- a/ch12/ch12.ipynb
+++ b/ch12/ch12.ipynb
@@ -696,6 +696,8 @@
     "        ------------\n",
     "        y : array, shape = [n_examples]\n",
     "            Target values.\n",
+    "        n_classes : int\n",
+    "            Number of classes\n",
     "\n",
     "        Returns\n",
     "        -----------\n",
@@ -1339,4 +1341,4 @@
  },
  "nbformat": 4,
  "nbformat_minor": 4
-}
+}
\ No newline at end of file
diff --git a/ch12/ch12.py b/ch12/ch12.py
index d581f644..f0225b7f 100644
--- a/ch12/ch12.py
+++ b/ch12/ch12.py
@@ -308,6 +308,8 @@ def _onehot(self, y, n_classes):
         ------------
         y : array, shape = [n_examples]
             Target values.
+        n_classes : int
+            Number of classes
 
         Returns
         -----------
diff --git a/ch12/neuralnet.py b/ch12/neuralnet.py
index 5d73bde7..a3d7a7d2 100644
--- a/ch12/neuralnet.py
+++ b/ch12/neuralnet.py
@@ -49,6 +49,8 @@ def _onehot(self, y, n_classes):
         ------------
         y : array, shape = [n_examples]
             Target values.
+        n_classes : int
+            Number of classes
 
         Returns
         -----------