gtk-socket

Hi.

I'm trying to use gtk-socket from guile but got following error:

(guile-2.0:18181): Gtk-CRITICAL **: IA__gtk_socket_get_id: assertion
'GTK_WIDGET_ANCHORED (socket)' failed

The code I use is:

(use-modules (oop goops) (gnome gobject) (gnome glib) (gnome gtk)  (gnome gobject utils))

(define notebook (make <gtk-notebook> #:enable-popup #t #:scrollable #t))

(define (hello)
  (let* ((main-window (make <gtk-window> #:type 'toplevel))
     (gsock1 (make <gtk-socket>))
     (gsock2 (make <gtk-socket>))
     (gsock3 (make <gtk-socket>))

    (connect main-window 'delete-event (lambda (w e) (gtk-main-quit) #f))
    (add main-window notebook)
    (append-page notebook gsock1
              (make <gtk-label> #:label (number->string (gtk-socket-get-id gsock1))
#:use-underline #t))
    (append-page-menu notebook gsock2
              (make <gtk-label> #:label (number->string (gtk-socket-get-id gsock2))
#:use-underline #t))
    (append-page-menu notebook gsock3
              (make <gtk-label> #:label (number->string (gtk-socket-get-id gsock3))
#:use-underline #t))
  
    (show-all main-window)
    (gtk-main)))

(hello)

I've got 3 tabs created as expected but the label on all 3 is 0 while I would expect
to see actual id uniq for each tab.

What's the right way to use gtk-socket? Are there some examples available somewhere?

cheers,
Max.