Window with WindowStaysOnTopHint covers its modal child dialog on Mac

Trying to move to Qt 5.2 from 4.8.5. Main window has WindowStaysOnTopHint flag, another modal dialog blocks interacation with main window, but is displayed underneath it. This behaviour didn't appear in Qt 4 and child dialogs "inherited" on-top behaviour.

Setting WindowStaysOnTopHint to the child dialog doesn't help.

The issue can be quickly reproduced with a couple of code lines. Please see the code below and the complete project is also attached.

#include <QMessageBox>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    connect(ui->pushButton, SIGNAL(clicked()), this, SLOT(onClicked()));

    setWindowFlags(windowFlags() | Qt::WindowStaysOnTopHint);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::onClicked()
{
    QMessageBox::information(this, "Title", "String");
}