ADF SelectOneChoice Required Validation

<af:selectOneRadio value="" id="sor1" required="true" autoSubmit="true" label="text">                          <f:selectItems value=""" id="si2"/>

</af:selectOneRadio>

• SelectOneChoice with no selection option as first item. It returns "" instead of NULL so required doesn't fire.
• one solution is to remove the no selection option.