[xml] problem with libxml2

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Hello!
I use libxml2 (29.05.02) for Win32 and have the following problem:
It doesn't understand any URL containing the space symbol. 

For example xmllint utility validating XML file, containing string 
	<!DOCTYPE MySchema SYSTEM "sub directory/test.dtd"> 
will generate error
	failed to load external entity...
whereas the same file without space ("subdirectory/...") processes OK.
(Both directories - "subdirectory" and "sub directory" exist and contain
files test.dtd)
Using the additional quotes - &quot; does not aid.

How can I avoid this problem? 
Using pathes with space symbol is obligatory for me - "c:\Documents and
Settings" and so on...
Thank you