about cp1251 and nsgmls

[Nikolay Hristov <geroy@stemo.bg>]

hello

I've translated debian new maintainer's guide, but when I run make I've got 
these errors:
$make
debiandoc2html -l bg maint-guide.bg.sgml
nsgmls:maint-guide.bg.sgml:19:99:E: non SGML character number 255
nsgmls:maint-guide.bg.sgml:34:36:E: non SGML character number 255
nsgmls:maint-guide.bg.sgml:37:15:E: non SGML character number 255
[ -------------- cut -----------]
nsgmls:maint-guide.bg.sgml:150:59:E: non SGML character number 255
nsgmls:maint-guide.bg.sgml:151:17:E: non SGML character number 255
make: *** [maint-guide.bg.html/index.html] Error 1

Is 255 is forbidden character in sgml or  this is bug in nsgmls validator?
Translation is in cp1251 encoding. When I convert it with iconv from
cp1251 -> iso8859-5, then run make and after that iconv again from 
iso8859-5 -> cp1251 everything is OK?
what can I do to solve that problem?

Nikolay Hristov