diff --git a/Tutorial.ipynb b/Tutorial.ipynb
index 9900f39..819afc9 100644
--- a/Tutorial.ipynb
+++ b/Tutorial.ipynb
@@ -1232,7 +1232,7 @@
     "    dx2 = 0\n",
     "    \n",
     "    #run backward\n",
-    "    dy,dx2  = sum_vjp(y,x1, dy, dx1, dz)\n",
+    "    dy,dx1  = sum_vjp(y,x1, dy, dx1, dz)\n",
     "    dx1,dx2 = mul_vjp(x1,x2, dx1, dx2, dy)\n",
     "    return z,[dx1,dx2]"
    ]