dconf build error

make[2]: Entering directory `/home/stefan/Gnome/code/dconf/editor'
  ITMRG  dconf-editor.desktop
  VALAC    dconf_editor_vala.stamp
dconf-model.vala:415.5-415.30: error: overriding method `KeyModel.iter_nth_child' is incompatible with base method `Gtk.TreeModel.iter_nth_child': incompatible direction of parameter 1.
    public bool iter_nth_child(ref Gtk.TreeIter iter, Gtk.TreeIter? parent, int n)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^
dconf-model.vala:349.31-349.38: error: Argument 1: Cannot pass out argument to non-output parameter
        return iter_nth_child(out iter, null, path.get_indices()[0]);
                              ^^^^^^^^
dconf-model.vala:706.5-706.30: error: overriding method `SettingsModel.iter_nth_child' is incompatible with base method `Gtk.TreeModel.iter_nth_child': incompatible direction of parameter 1.
    public bool iter_nth_child(ref Gtk.TreeIter iter, Gtk.TreeIter? parent, int n)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^
dconf-model.vala:649.29-649.36: error: Argument 1: Cannot pass out argument to non-output parameter
        if (!iter_nth_child(out iter, null, path.get_indices()[0]))
                            ^^^^^^^^
dconf-model.vala:537.5-537.30: error: overriding method `EnumModel.iter_nth_child' is incompatible with base method `Gtk.TreeModel.iter_nth_child': incompatible direction of parameter 1.
    public bool iter_nth_child(ref Gtk.TreeIter iter, Gtk.TreeIter? parent, int n)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^
dconf-model.vala:487.31-487.38: error: Argument 1: Cannot pass out argument to non-output parameter
        return iter_nth_child(out iter, null, path.get_indices()[0]);
                              ^^^^^^^^
dconf-view.vala:169.9-169.25: warning: Gtk.CellRenderer.get_size has been deprecated since 3.0. Use get_preferred_size
dconf-model.vala:715.5-715.27: error: overriding method `SettingsModel.iter_parent' is incompatible with base method `Gtk.TreeModel.iter_parent': incompatible direction of parameter 1.
    public bool iter_parent(ref Gtk.TreeIter iter, Gtk.TreeIter child)
    ^^^^^^^^^^^^^^^^^^^^^^^
dconf-editor.vala:382.36-382.43: error: Argument 1: Cannot pass out argument to non-output parameter
            if (!model.iter_parent(out iter, iter))
                                   ^^^^^^^^
Compilation failed: 8 error(s), 1 warning(s)
make[2]: *** [dconf_editor_vala.stamp] Fehler 1
make[2]: Leaving directory `/home/stefan/Gnome/code/dconf/editor'
make[1]: *** [all-recursive] Fehler 1
make[1]: Leaving directory `/home/stefan/Gnome/code/dconf'
make: *** [all] Fehler 2