XSL-FO: TOC and international characters

Hello to all,

I'm using Docbook, XSL-FO, FOP tool chain to create
 a PDF document. I've managed to tune everything except one thing: 
international characters that I use in sections'  titles do not appear 
right in PDF document.

Looking around, I've found that my FO document already misses 
(almost) all international characters in TOC - they are translated into 
ASCII characters. The rest of the FO document is all right.

Checking
 XSL-FO *.xsl scripts I've found fop1.xsl which seems to translate 
(almost) all international characters to their ASCII equivalents. I've 
verified that when the translation is removed the FO document contains 
the international characters and the generated PDF document is all 
right.

I'm just wondering why the translation takes place in TOC 
generation. Is there a good reason for this? Can I turn this translation
 off without hacking fop1.xsl? 

I'm using XSL-FO version 1.75.2.

Thanks for answer and/or advice. And many thanks for your wonderful  XSL-FO!

Pavel