Problema com h:selectOneRadio + f:ajax

Galera, simplifiquei o código mas a essência é a mesma, não consigo renderizar um campo via ajax jsf2… estou fazendo algo errado??? Segue abaixo o código:


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:ui="http://java.sun.com/jsf/facelets"
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:f="http://java.sun.com/jsf/core">

		<h:form id="comprasForm" prependId="false">
			<h:selectOneRadio value="#{compraBean.codigo}">
				<f:selectItem itemValue="1" itemLabel="Sim"/>
				<f:selectItem itemValue="2" itemLabel="Nao"/>
				 <f:ajax event="change" execute="@this" render="desconto" />
			</h:selectOneRadio> Compra com desconto
			<h:panelGroup id="desconto">
				<h:panelGroup rendered="#{compraBean.codigo == 1}">
					     10% desconto 
				</h:panelGroup>
			</h:panelGroup>
		</h:form>
</html>  

@RequestScoped
@Named
public class CompraBean {
	
	private Integer codigo;
	
	public Integer getCodigo() {
		return codigo;
	}
	
	public void setCodigo(Integer codigo) {
		this.codigo = codigo;
	}
	
}