[Vaadin 6] Error indicator and liferay theme


I’m develpoing a portlet with vaadin 6.8.14 for liferay 6.1.3 CE useing the liferay theme. My problem is, that if I use setComponentError to indicate an error e.g. in a textbox there is no indicator in the liferay theme, but if I use an other theme threre is. The overlay with the error message is there, it also gets showen if I put the mouse over the component, but there is no “!”.
What to do?