Menu2 onUpdate(dc) function never called.

I have a class Menu2 on top of the view stack. Simplified it looks like this:

using Toybox.WatchUi;

class MainMenu extends WatchUi.Menu2 {

    function initialize(opt) {
        Menu2.initialize(opt);
    }

    function onUpdate(dc) {
        System.println("onUpdate");
        setTitle("New Title");
        View.onUpdate(dc);
    }

    function onShow() {
        System.println("onShow");
        setTitle("Title");
    }
}

I noticed that the onUpdate function is never called. I tried to trigger it with a
WatchUi.requestUpdate();
When running in the simulator, the println for onUpdate is never printed, the one for onShow is at some point. The API documentation states that Menu2 inherits form View. Anyone who can give a hint why my onUpdate function is never called?