src/main/java/org/efaps/ui/wicket/components/table/header/HeaderCellPanel.java
@Override
    protected void onAfterRender()
    {
        super.onAfterRender();
        if (getDefaultModel() != null) {
            final UITableHeader headermodel = (UITableHeader) getDefaultModelObject();
            headermodel.setMarkupId(this.getMarkupId());
        }
    }
@Override
    protected void onAfterRender()
    {
        super.onAfterRender();
        if (getDefaultModel() != null) {
            final UITableHeader headermodel = (UITableHeader) getDefaultModelObject();
            headermodel.setMarkupId(this.getMarkupId());
        }
    }
Set the markupid into the model.

@see org.apache.wicket.Component#onAfterRender()