Unable to quit on mac when setQuitOnLastWindowClosed = false after last window is closed

#include <QApplication>
#include <QMainWindow>
#include <QLabel>
#include <QMenuBar>
#include <QMenu>

// To reproduce: 
// 1. Run app
// 2. Close main window with close button on caption bar
// 3. Try to exit via the application menu or Cmd-Q
//
// EXPECTED: application quits
// ACTUAL: unable to quit

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

	// Create the global menu which we will revert to when the QMainWindow is closed
	QMenuBar* sharedMenuBar=new QMenuBar(0); 
	QMenu* sharedMenu= sharedMenuBar->addMenu("Shared menu");
	sharedMenu->addAction("Nop");

	// Create an Exit menu item which will be moved to the application menu
	QAction* exitAct = sharedMenu->addAction("E&xit");
	exitAct->setMenuRole(QAction::QuitRole);
	sharedMenu->addAction(exitAct);

	// Workaround is to uncomment the following line:
	// QObject::connect(exitAct, SIGNAL(triggered()), &app, SLOT(quit()));

	// Now create the main window and create a simple menu for it
	QMainWindow mainWindow;
	QLabel* staticText=new QLabel("Hit the close button to close this window then type cmd-Q");
	mainWindow.setCentralWidget(staticText);
	QMenu* mainWindowFileMenu= mainWindow.menuBar()->addMenu("Window menu");
	mainWindowFileMenu->addAction("Nop");

	mainWindow.show();

	return app.exec();
}