How to set an Accelerator for a MenuButton in JavaFX?

Question

How can I attach an Accelerator to a MenuItem inside a MenuButton (using JavaFX 2.2)? I tried it the following way:

public class Minimal extends Application
{
@Override
public void start(Stage primaryStage) throws Exception
{
    primaryStage.setScene(SceneBuilder.create()
        .root(StackPaneBuilder.create()
            .children(MenuButtonBuilder.create()
                  .text("MenuButton")
                  .items(
                    MenuItemBuilder.create()
                      .text("MenuItem A")
                      .accelerator(new KeyCodeCombination(KeyCode.B, KeyCombination.ALT_DOWN))
                      .onAction(new EventHandler<ActionEvent>() {
                          @Override public void handle(ActionEvent e) {
                            System.out.println(e.getEventType() +
                                               " occurred on Menu Item A");
                          }
                        })
                      .build()
                   )
                  .build())
            .build())
        .build());
    primaryStage.show();
}

public static final void main(String[] args)
{
    Minimal.launch(args);
}

}

It compiles fine but gives me an exception at runtime when I press the KeyCombination. Selecting the MenuItem with the mouse works as expected. Here's the exception (there are more method calls in the stack trace, but none of them is from my application):

java.lang.NullPointerException
    at com.sun.javafx.scene.control.skin.MenuButtonSkinBase$5.run(MenuButtonSkinBase.java:306)
    at com.sun.javafx.scene.KeyboardShortcutsHandler.processAccelerators(KeyboardShortcutsHandler.java:296)
    at com.sun.javafx.scene.KeyboardShortcutsHandler.dispatchBubblingEvent(KeyboardShortcutsHandler.java:119)

Since the Stack trace says 'MenuButtonSkinBase', it tried disabling all custom styles I use, but no luck.

Edit: Here is the jdk version output i used to compile the code:

java version "1.7.0_07"
Java(TM) SE Runtime Environment (build 1.7.0_07-b11)
Java HotSpot(TM) Client VM (build 23.3-b01, mixed mode, sharing)

Thanks in advance!