String-based QObject::connect asserts when parameters are incomplete types

#include <QObject>

class Sender : public QObject
{
    Q_OBJECT

signals:
    void contentsChanged(const QImage &);
};

class Receiver : public QObject
{
    Q_OBJECT

public slots:
    void updateContents(const QImage &img) { }
};

int main(int argc, char *argv[])
{
    Sender sender;
    Receiver receiver;

    QObject::connect(&sender, SIGNAL(contentsChanged(QImage)),
                     &receiver, SLOT(updateContents(QImage)));
}

#include "main.moc"

ASSERT: "typeInfo & IsUnresolvedType || typeInfo == QMetaType::Void" in file /Users/vohi/qt/dev/qtbase/src/corelib/kernel/qmetaobject.cpp, line 1825