diff --git a/notebooks/2015-06-20-export-to-xdmf.ipynb b/notebooks/2015-06-20-export-to-xdmf.ipynb
index ba5a892..3475f0f 100644
--- a/notebooks/2015-06-20-export-to-xdmf.ipynb
+++ b/notebooks/2015-06-20-export-to-xdmf.ipynb
@@ -148,6 +148,13 @@
     "topology.insertAsInt32(0, [0x6, 1, 2, 3, 4]) # Not sure starts this from 0 or 1"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**update**, node numbering starts from 0."
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 10,
diff --git a/testdata/xdmf_1tet/testdata.xmf b/testdata/xdmf_1tet/testdata.xmf
index 652a40f..697fd3a 100644
--- a/testdata/xdmf_1tet/testdata.xmf
+++ b/testdata/xdmf_1tet/testdata.xmf
@@ -10,7 +10,7 @@
           <DataItem DataType="Float" Dimensions="12" Format="XML" Precision="4">0 0 0 1 0 0 0 1 0 0 0 1</DataItem>
         </Geometry>
         <Topology Dimensions="1" Type="Mixed">
-          <DataItem DataType="Int" Dimensions="5" Format="XML" Precision="4">6 1 2 3 4</DataItem>
+          <DataItem DataType="Int" Dimensions="5" Format="XML" Precision="4">6 0 1 2 3</DataItem>
         </Topology>
         <Attribute Center="Cell" Name="Temperature field" Type="Scalar">
           <DataItem DataType="Int" Dimensions="1" Format="XML" Precision="4">56</DataItem>