Impossible to cancel the deletion of a document in a listener

/**
 * @version $Id: $
 */
@Component
@Named("SomeName")
@Singleton
public class ProtectedPages implements EventListener
{
    private static final List<Event> EVENTS = Arrays.<Event>asList(new DocumentDeletingEvent());

    private static final List<DocumentReference> PROTECTED_PAGES = Arrays.asList(
            new DocumentReference("xwiki", "XWiki", "SomePage1"),
            new DocumentReference("xwiki", "XWiki", "SomePage2")
    );

    @Inject
    private Logger logger;

    @Override
    public String getName()
    {
        return "Some Name";
    }

    @Override
    public List<Event> getEvents()
    {
        return EVENTS;
    }

    @Override
    public void onEvent(Event event, Object source, Object data)
    {
        XWikiDocument document = (XWikiDocument) source;
        DocumentReference documentReference = document.getDocumentReference();
        if (PROTECTED_PAGES.contains(documentReference)) {
            if (event instanceof CancelableEvent) {
                CancelableEvent cancelableEvent = (CancelableEvent) event;
                cancelableEvent.cancel("This document must be present in the wiki.");
            } else {
                logger.error("Failed to cancel the event [{}] for the document [{}].", event, documentReference);
            }
        }
    }
}