QTextCodec::codecForName("System") returns NULL in windows when compiled with ICU

I have compiled Qt for windows 64 in mingw64 with ICU support.

Attempting then to use "System" codec in QTextCodec::codecForName ("System"), returns null.

However, using: QTextCodec::codecForLocale(); returns codec "windows-1252"

Codewise:

 QTextCodec * d1 = QTextCodec::codecForName ("System");
 qDebug("%s", d1 ? qPrintable(d1->name()) : "<null>"); // currently prints "<null>"
 
 QTextCodec * d2 = QTextCodec::codecForLocale();
 qDebug("%s", d2 ? qPrintable(d2->name()) : "<null>"); // currently prints "windows-1252"

 
I would expect both to be the same? and at least not NULL, for the System.