gtk-can-change-accels property absent in gtk 2.8.20?

[Richard Shann <richard shann virgin net>]

I tried to putting a line to set the gtk-can-change-accels property
thus:

  g_object_set (gtk_settings_get_for_screen (gdk_screen_get_default ()),
                "gtk-can-change-accels",TRUE,
                NULL);
I put this in just after gtk_init and got the runtime warning

(denemo:10714): GLib-GObject-WARNING **: IA__g_object_set_valist: object
class `GtkSettings' has no property named `gtk-can-change-accels'

The versions are
glib 2.12.4 
gtk 2.8.20

and the docs for http://library.gnome.org/devel/gtk/2.8/
say there should be such a property.
Any ideas?

Richard Shann