Slick2D, Nifty GUI interaction problem

Hello all!

I'm trying to get Nifty to work with Slick2D. So far everything is going great, except that I can't seem to figure out how to properly interact with the GUI. I'm trying the example in the nifty manual http://sourceforge.n....0.pdf/download
but it doesn't seem to entirely work. The Element controller is being called for bind(...), init(...) and onStartScreen() as it should, as I can see their println output, but the next() method isn't being called when I click on the GUI element that I assigned the controller to, nor the screen controller as no println is shown.
It's supposed to be called when I click the mouse button on it from the in the XML.

Here is my code:

My Element controller:

public class ElementController implements Controller {

private Element element;

@Override
public void bind(Nifty nifty, Screen screen, Element element, Properties parameter, Attributes controlDefinitionAttributes) {
this.element = element;
System.out.println("bind() called for element: " + element);
}

@Override
public void init(Properties parameter, Attributes controlDefinitionAttributes) {
System.out.println("init() called for element: " + element);
}

@Override
public void onStartScreen() {
System.out.println("onStartScreen() alled for element: " + element);
}

@Override
public void onFocus(boolean getFocus) {
System.out.println("onFocus() called for element: " + element + ", with: " +
getFocus);
}

@Override
public boolean inputEvent(NiftyInputEvent inputEvent) {
return false;
}

public void next() {
System.out.println("next() clicked for element: " + element);
}
}


MyScreenController:

class MyScreenController implements ScreenController {
public void bind(Nifty nifty, Screen screen) {}
public void onEndScreen() {}
public void onStartScreen() {}
public void next() {
System.out.println("next() called from MyScreenController");
}
}


And my XML file:

<?xml version="1.0" encoding="UTF-8"?>
<nifty xmlns="http://nifty-gui.sourceforge.net/nifty-1.3.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://niftygui.sourceforge.net/nifty-1.3.xsd http://nifty-gui.sourceforge.net/nifty-1.3.xsd">
<screen id="start" controller="predaN00b.theThing.V0004.MyScreenController">
<layer childLayout="center" controller="predaN00b.theThing.V0004.ElementController">
<panel width="100px" height="100px" childLayout="vertical" backgroundColor="#ff0f">
<text font="aurulent-sans-16.fnt" color="#ffff" text="Hello World!">
<interact onClick="next()" />
</text>
</panel>
</layer>
</screen>
</nifty>


My main class, in case it's needed:
My main class:

public class MainGameState extends BasicGame {

public Nifty nifty;

public MainGame() {
super("Test");
}

public void init(GameContainer container, StateBasedGame game) throws SlickException {

nifty = new Nifty(new SlickRenderDevice(container), new NullSoundDevice(), new PlainSlickInputSystem(), new AccurateTimeProvider());

nifty.addXml("/xml/MainState.xml");
nifty.gotoScreen("start");

}

public void update(GameContainer container, StateBasedGame game, int delta) throws SlickException {
nifty.update();
}

public void render(GameContainer container, StateBasedGame game, Graphics graphics) throws SlickException {
nifty.render(false);
}

public static void main(String[] args) throws SlickException {
AppGameContainer app = new AppGameContainer(new MainGame());
app.setAlwaysRender(true);
app.setDisplayMode( 1260 , 720, false); //window size
app.start();
}
}