Compile POCO with UTF8 support

I'm compiling POCO 1.5 version with

#define POCO_WIN32_UTF8

in Config.h. As I can read in docs, with this flag I'm enabling UTF8 support, but when I go to File_WIN32.cpp I can see how in createFileImpl() there is one call to CreateFileA() function (win ascii version of this function) not call to CreateFileW(). Where I am wrong? Any other flag to activate?