Selectitem with listgrid: Does not launch getCellCSSText method

Passage from my code:

...
SelectItem selectitem = new SelectItem();
ListGrid pickListProperties = new ListGrid() {
@Override
protected String getCellCSSText(ListGridRecord record, int rowNum, int colNum) {
return "font-weight:bold; color: yellow; background-color: Lightblue; ";
}
};
selectitem.setPickListProperties(pickListProperties);
...

Why, does not trigger getCellCSSText method ?

SmartGWT 4.0
Chromium Version 24.0.1312.52 (175374) (linux)