diff --git a/tutorials/User-Defined-Model/User-Defined-Model.ipynb b/tutorials/User-Defined-Model/User-Defined-Model.ipynb
index b9a941bb..a20cfa46 100644
--- a/tutorials/User-Defined-Model/User-Defined-Model.ipynb
+++ b/tutorials/User-Defined-Model/User-Defined-Model.ipynb
@@ -769,9 +769,9 @@
     "    \n",
     "    @staticmethod\n",
     "    def fit_deriv(x, a, b, c, d):\n",
-    "        d_a = np.sin(b*x+c)+d\n",
+    "        d_a = np.sin(b*x+c)\n",
     "        d_b = a*np.cos(b*x+c)*x\n",
-    "        d_c = a*np.sin(b*x+c)\n",
+    "        d_c = a*np.cos(b*x+c)\n",
     "        d_d = np.ones(x.shape)\n",
     "        return [d_a, d_b, d_c, d_d]"
    ]