QTextEdit "alt" tag regression from Qt3

Running the Qt4 test case below results in the loss of the "alt" tag, whereas in the Qt3 version it doesn't happen.

Qt4 test case:
//----------------------
#include <QtGui>

class Test: public QMainWindow
{
public:
Test( QWidget * parent = 0 )
: QMainWindow( parent )

{ QTextEdit * edit = new QTextEdit( this ); setCentralWidget( edit ); QString html = "<img src='foo' alt='stuff:0:0'>"; edit->setHtml( html ); qDebug() << "Html in : " << html; qDebug() << "Html out: " << edit->toHtml(); }

};

int main( int argc, char * argv[] )
{
QApplication a( argc, argv );
Test t;
t.resize( 700, 800 );
t.show();
return a.exec();
}

Qt3 test case:
//----------------------
#include <qapplication.h>
#include <qmainwindow.h>
#include <qtextedit.h>

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

{ QTextEdit * edit = new QTextEdit( this ); setCentralWidget( edit ); QString html = "<img src='foo' alt='stuff:0:0'>"; edit->setTextFormat(Qt::RichText); edit->setText( html ); qDebug("Html in : %s \n", html.latin1() ); qDebug("Html out: %s \n", edit->text().latin1()); }

};

int main( int argc, char * argv[] )
{
QApplication a( argc, argv );
Test t;
t.resize( 700, 800 );
t.show();
return a.exec();
}