Can I update #{invalid} in the s:decorate after an ajax proc

[wuhaixing]

I have the following s:decorate template as a form row template

<div class="formRow">
<a4j:region id="#{fieldId}Field" selfRendered="true" regionRenderOnly="true">
 <ui:insert/>
 <div id="#{fieldId}Label" class="formlabel #{invalid?'errlabel':''}">
 <ui:insert name="label"/>
 </div>

 <div id="#{fieldId}Input" class="formfield #{invalid?'flderr':''}">
 <ui:insert name="field"/>
 <a4j:status for="#{fieldId}Field">
 <f:facet name="start">
 <h:graphicImage value="/img/ajax_process.gif"/>
 </f:facet>
 </a4j:status>
 </div>

 <a4j:outputPanel id="#{fieldId}MessageBlock" layout="block" styleClass="errorMsg" ajaxRendered="true" rendered="#{invalid}">
 <s:message for="#{fieldId}" globalOnly="false"/>
 </a4j:outputPanel>
</a4j:region>

</div>

and a form row like this:

<s:decorate id="emailFormRow" template="/layout/formRow.xhtml">
 <ui:define name="label">
 <h:outputLabel for="email" value="#{messages['register.email']}"/>
 </ui:define>
 <ui:define name="field">
 <h:inputText id="email" value="#{member.email}" required="true">
 <a4j:support event="onchange" reRender="emailMessageBlock" requestDelay="0" ajaxSingle="true"/>
 </h:inputText>
 </ui:define>
 <ui:param name="fieldId" value="email"/>
 </s:decorate>

but after ajax process,the a4j:outputPanel cann't display anyway.
Is it an a4j's bug?