RadioGroupItem bug

I think I found a bug with this componenet.
I wrote the following code:

final RadioGroupItem showActive = new RadioGroupItem();
		showActive.setVertical(false);
		showActive.setTitle(messages.labelShowOnlyActive());
		LinkedHashMap<String, String> yesNo = new LinkedHashMap<String, String>();
		yesNo.put("1", messages.labelYes() );
		yesNo.put("0", messages.labelNo() );
		showActive.setValueMap(yesNo);
		showActive.setDefaultValue("0");
		showActive.setColSpan(2);
        showActive.setCellStyle("customRadioCell");

but the cell’s class are still set to formCell …