qgraphicsitem_cast cannot convert seft-defined types

[Seishin]

I have a class inherits QGraphicsRectItem with type function

int RectItem::type() const
{
	return UserType + 1; 
}

int RectItem::type() const
{
	return UserType + 1; 
}

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But when I try to coverting a QGraphicsItem pointer to RectItem pointer, the qgraphicsitem_cast returns null.

QList<QGraphicsItem *> items = scene()->selectedItems();
for(int i=0; i<items.size(); i++){
	if(items[i]->type() == UserType + 1)
		RectItem*rectItem = qgraphicsitem_cast<RectItem*>(items[i]);

QList<QGraphicsItem *> items = scene()->selectedItems();
for(int i=0; i<items.size(); i++){
	if(items[i]->type() == UserType + 1)
		RectItem*rectItem = qgraphicsitem_cast<RectItem*>(items[i]);

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Here rectItem is null. However if I change the cast to dynamic_cast, the convertion will be successful.

QList<QGraphicsItem *> items = scene()->selectedItems();
for(int i=0; i<items.size(); i++){
	if(items[i]->type() == UserType + 1){
		RectItem*rectItem = dynamic_cast<RectItem*>(items[i]);

QList<QGraphicsItem *> items = scene()->selectedItems();
for(int i=0; i<items.size(); i++){
	if(items[i]->type() == UserType + 1){
		RectItem*rectItem = dynamic_cast<RectItem*>(items[i]);

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Here rectItem is the real RectItem selected.

Anyone knows why qgraphicsitem_cast is not working?
Thanks in advance.