a Close button too many

Sorry if this is not a CLG specific question; it may just be that I'm
not understanding GTK itself.

I'm trying to write a yes/no dialog with this code:

(let* ((response nil)
       (dialog (make-instance 'message-dialog
			:message-type :question
			:button '("gtk-yes" :yes)
			:button '("gtk-no" :no)
			:text message
			:signal (list 'response #'(lambda (dialog id)
						    (setf response (dialog-find-response dialog id)))
			:object t))))
    (dialog-run dialog)
    (widget-destroy dialog)
    (eq response :yes))


But contrary to my expectations I don't get two buttons but three.
How do I get rid of the Close button?

Cheers,

-- 
walter pelissero
http://www.pelissero.de

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