JLabel ToolTip interferes with MouseListener

Question

I have Java Swing application ToolTipMouseTest

The critical line is label.setToolTipText("label" + i);. Once it is commented out very click on a label produces 2 mousePressed in console. With this line enabled click on labels would produce nothing.

Is this expected behaviour or a bug? My goal is to show tooltips without disabling MouseListener from working.

Almost SSCCE, but without imports:

public class ToolTipMouseTest {

public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            new ToolTipMouseTest();
        }
    });
}

public ToolTipMouseTest() {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLayout(new BorderLayout());

    JLayeredPane lpane = new JLayeredPane() {
        @Override
        public Dimension getPreferredSize() {
            return new Dimension(600,400);
        }
    };

    MouseAdapter1 mouseAdapter1 = new MouseAdapter1();
    lpane.addMouseListener(mouseAdapter1);

    frame.add(lpane);

    JPanel panel1 = new JPanel();
    panel1.setSize(new Dimension(600, 400));
    panel1.setOpaque(false);

    lpane.add(panel1, JLayeredPane.PALETTE_LAYER);

    JPanel panel2 = new JPanel();
    for (int i = 0; i < 5; i++) {
        JLabel label = new JLabel("Label " + i);
        panel2.add(label);
        label.setToolTipText("label" + i); //HERE!!
    }

    JScrollPane spane = new JScrollPane(panel2) {
        private static final long serialVersionUID = 1L;

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(300, 200);
        }
    };

    MouseAdapter2 mouseAdapter2 = new MouseAdapter2();
    spane.addMouseListener(mouseAdapter2);

    panel1.add(spane);

    frame.pack();
    frame.setVisible(true);
}

private class MouseAdapter1 extends MouseAdapter {
    @Override
    public void mousePressed (MouseEvent me) {
        System.out.println("1 mousePressed");
    }
}

private class MouseAdapter2 extends MouseAdapter {
    @Override
    public void mousePressed (MouseEvent me) {
        System.out.println("2 mousePressed");
    }
}
}