Setting child properties with GtkBuilder

[Cedric Sodhi <manday gmx net>]

Hello,

I'm trying to build a tabular interface with GtkBuilder, using GtkGrid.

GtkGrid specifies that it provides child properties left-attach and
top-attach and they do in fact exist, but whenever I attempt to set them
by

<object class="GtkGrid">
 <child>
  <object class="GtkLabel">
	 <property name="left-attach">0</property>
  </object>
 </child>
</object>

GtkBuilder says that "Unknown property: GtkLabel.left-attach"

Could anyone help with that?

Thanks.