diff --git a/xarray/core/datatree.py b/xarray/core/datatree.py
index 6289146308e..6241d79f83f 100644
--- a/xarray/core/datatree.py
+++ b/xarray/core/datatree.py
@@ -770,7 +770,7 @@ def _replace_node(
         if data is not _default:
             self._set_node_data(ds)
 
-        self._children = children
+        self.children = children
 
     def copy(
         self: DataTree,
diff --git a/xarray/tests/test_datatree.py b/xarray/tests/test_datatree.py
index c875322b9c5..9a15376a1f8 100644
--- a/xarray/tests/test_datatree.py
+++ b/xarray/tests/test_datatree.py
@@ -245,6 +245,7 @@ def test_update(self):
         dt.update({"foo": xr.DataArray(0), "a": DataTree()})
         expected = DataTree.from_dict({"/": xr.Dataset({"foo": 0}), "a": None})
         assert_equal(dt, expected)
+        assert dt.groups == ("/", "/a")
 
     def test_update_new_named_dataarray(self):
         da = xr.DataArray(name="temp", data=[0, 50])