Can't see signals or slots in Locals and Expressions view

http://qt-project.org/doc/qtcreator-3.0/creator-tips.html says:

If an instance of a class is derived from QObject, and you would like to find all other objects connected to one of your object's slots using Qt's signals and slots mechanism, select Tools > Options > Debugger > Debugging Helper > Use Debugging Helper.

In the Locals and Expressions view, expand the object's entry and open the slot in the slots subitem. The objects connected to this slot are shown as children of the slot. This method works with signals too.

I checked that this is enabled, and it is.

I then put a breakpoint on the app.exec() line of the following code:

#include <QApplication>

class Object : public QObject
{
    Q_OBJECT
public:
    Object() {}

public slots:
    void aSlot() {}
signals:
    void aSignal();
};

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

    Object o;

    QObject::connect(&o, SIGNAL(aSignal()), &o, SLOT(aSlot()));

    return app.exec();
}

#include "main.moc"