QRadiobutton in Q3ButtonGroup does not emit clicked()

The first radio button in the cole below does not emit the clicked() signal. A Qt 3 version of the same code works perfectly.

// ----------------------------------------------------
#include <Qt3Support>
#include <QtGui>

class Button : public Q3ButtonGroup
{
Q_OBJECT

public:
Button( QWidget * parent ) : Q3ButtonGroup( parent, "dd" )

{ QHBoxLayout * l = new QHBoxLayout( this ); b1 = new QRadioButton( "I don't work", this ); b2 = new QRadioButton( "I work", this ); b3 = new QRadioButton( "I work", this ); l->addWidget( b1 ); l->addWidget( b2 ); l->addWidget( b3 ); connect( b1, SIGNAL( clicked() ), this, SLOT( btnClicked() ) ); connect( b2, SIGNAL( clicked() ), this, SLOT( btnClicked() ) ); connect( b3, SIGNAL( clicked() ), this, SLOT( btnClicked() ) ); }

public slots:
void btnClicked()

{ qDebug() << "Clicked!"; }

private:
QAbstractButton * b1, * b2, * b3;
};

class Test : public Q3MainWindow
{
public:
Test( QWidget * parent = 0, const char * name = 0 )
: Q3MainWindow( parent, name, 0 )

{ Button * b = new Button( this ); setCentralWidget( b ); }

};

int main( int argc, char * argv[] )
{
QApplication app( argc, argv );
Test test;
test.show();
return app.exec();
}

#include "main.moc"
// ----------------------------------------------------