xml:base and stylesheets

I notice that the DocBook XSL stylesheets seem to be throwing away the 
xml:base attributes that my XInclude processor inserts. Consequently 
images and other links are breaking. Is there any way to make the 
stylesheets respect and maintain xml:base? Or alternately use xml:base 
to fix up relative URLs when generating xml:baseless HTML or XHTML?

-- 
Elliotte Rusty Harold  
XML in a Nutshell 3rd Edition Just Published!
http://www.cafeconleche.org/books/xian3/
http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/ref=nosim