QLineEdit hexadecimal input mask accepts some invalid characters

Running the code below should result in the validation of hexadecimal characters only (0-9 and A-F).
However, characters like ALT+0178 ( ² ) ALT+0179 ( ³ ) are still accepted.

Code to reproduce:
//---------------------------------
#include <QtGui>

int main( int argc, char * argv[] )
{
QApplication app( argc, argv );

QDialog * dlg = new QDialog;
QHBoxLayout * lout = new QHBoxLayout( dlg );
QLineEdit * ledit = new QLineEdit( dlg );

lout->addWidget( ledit );
ledit->setInputMask( "HH:HH:HH" );
dlg->show();

return app.exec();
}
//---------------------------------