diff --git a/05_support_vector_machines.ipynb b/05_support_vector_machines.ipynb
index aa85276..687d74b 100644
--- a/05_support_vector_machines.ipynb
+++ b/05_support_vector_machines.ipynb
@@ -1017,7 +1017,8 @@
     "    boundary_x2s = -x1s*(w[0]/w[1])-b/w[1]\n",
     "    margin_x2s_1 = -x1s*(w[0]/w[1])-(b-1)/w[1]\n",
     "    margin_x2s_2 = -x1s*(w[0]/w[1])-(b+1)/w[1]\n",
-    "    ax.plot_surface(x1s, x2, 0, color=\"b\", alpha=0.2, cstride=100, rstride=100)\n",
+    "    ax.plot_surface(x1s, x2, np.zeros_like(x1),\n",
+    "                    color=\"b\", alpha=0.2, cstride=100, rstride=100)\n",
     "    ax.plot(x1s, boundary_x2s, 0, \"k-\", linewidth=2, label=r\"$h=0$\")\n",
     "    ax.plot(x1s, margin_x2s_1, 0, \"k--\", linewidth=2, label=r\"$h=\\pm 1$\")\n",
     "    ax.plot(x1s, margin_x2s_2, 0, \"k--\", linewidth=2)\n",