code: @Override
      protected void onAfterRender()
      {
          super.onAfterRender();
          if (getDefaultModel() != null) {
              final UITableHeader headermodel = (UITableHeader) getDefaultModelObject();
              headermodel.setMarkupId(this.getMarkupId());
          }
      }
docs: Set the markupid into the model.
  
  @see org.apache.wicket.Component#onAfterRender()