Delay in Tree ItemClickListener

I find it rather odd that clicking 1 on the tree is not observed until I click 2. Or is that not the intent of these listener as oppose Valuechangelistener?



	Window mainWindow = new Window();
		VerticalLayout demolay = new VerticalLayout();
		
		Tree tree  = new Tree();
		tree.addItem(1);
		tree.addItem(2);
		
		tree.setImmediate(true);
		tree.addListener(new ItemClickListener() {
			private static final long serialVersionUID = 1L;

			@Override
			public void itemClick(ItemClickEvent event) {
				System.out.println(event.getItemId());
			}
		});
		
		mainWindow.addComponent(tree);
		setMainWindow(mainWindow);

Just saw that tree.setNullSelectionAllowed(false); solves the problem, Nevertheless …