Not valid html output

Hello.

I validate html output of DocBook XSL Stylesheets 1.61.3
(documents are DocBook XML 4.2) with http://validator.w3.org/
and it's report what pages are invalid - no DOCTYPE specified.

Actually html output is not HTML 4.01 Strict, but HTML 4.01
Transitional.

It's possible to change default values of
"chunker.output.doctype-public"
"chunker.output.doctype-system"
from '' to corresponding values?

-- 
Regards, Vyt
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