XEmacs nox11 startup issue

All,

on a machine without X11 installation, I have upgraded XEmacs to 
21.4.23 and the packages. Now, xemacs (compiled without X11 support) 
gives me a 

Symbol's value as variable is void: default-menubar

unless started with either -vanilla or -no-init-file. OTOH, 
-no-site-file doesn't help, and -debug-init comes up empty. The 
constant 'default-menubar' shows up only in a few places

%  find ./xemacs* -name "*.el" -exec fgrep -l 'default-menubar' \{\} \;
./xemacs/xemacs-packages/lisp/Sun/sunpro-menubar.el
./xemacs/xemacs-packages/lisp/ediff/ediff-wind.el
./xemacs/xemacs-packages/lisp/guided-tour/guided-tour.el
./xemacs/xemacs-packages/lisp/ispell/ispell.el
./xemacs/xemacs-packages/lisp/w3/w3-menu.el
./xemacs-21.4.23/lisp/menubar-items.el
./xemacs-21.4.23/lisp/menubar.el
%

Where do I look next?

Cheerio,
Hauke

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