DOCBOOK-APPS: remove "Chapter" from titles

I don't want "Chapter" to appear in all the chapter titles. In dbparam.dsl I 
found:
(define %chap-app-running-head-autolabel% #t)

I changed to #f, but it had no effect. How can I remove "Chapter" from the 
titles?

As a solution I also tried to add label="" to all <chapter> tags, but that 
resulted in the first digit in the enumeration was removed in all the section 
titles. Kinda weird I'd say  :-)

Cheers,
Tim