Hello, I'm having a little problem with using conditionally evaluated expression in jsf/a4j

Here's my code

<a4j:form>
         <h:inputText id="id1" value="#{mybean.myvalue}" size="1"
                   required="#{not mybean.condition}"
                   rendered="#{not mybean.condition}"
                   requiredMessage="Put a number in here" />

           <h:selectBooleanCheckbox value="#{mybean.condition}">
                <a4j:support event="onclick" reRender="id1"/>
            </h:selectBooleanCheckbox>

<a4j:commandButton action="#{mybean.myaction}" value="Do something" />

 </a4j:form>

The boolean checkbox conditionally enable/disable the validation.

This doesn't work: the a4j:commandButton simply skip the validation.

Thanks.