immediate="true" on both input component and command component doesn't trigger required="true" on input component

Question

My sample form is given blow. When I click on the "Login" button, validation message is shown for the userName field as immediate="true". And when I click on the "Forgot Password" button, page is directed to my success page. As immediate=true present for button and userName input field, I am expecting required field validation on user name. But this is not the case.

Am I missing anything in this code?

<h:form>
    <h:panelGrid columns="3">
        <h:outputText value="User Name" for="userName" />
        <h:inputText id="userName" value="#{myBean.userName}" required="true"
            requiredMessage="User Name is required" immediate="true"
            binding="#{myBean.userNameText}"></h:inputText>
        <h:message for="userName" />
        <h:outputText value="User Password" for="userPwd" />
        <h:inputText id="userPwd" value="#{myBean.userPwd}" required="true"
            requiredMessage="User Password is required"
            binding="#{myBean.userPwdText}">
        </h:inputText>
        <h:message for="userPwd" />
        <h:commandButton value="Login" action="#{myBean.action()}"></h:commandButton>
        <h:commandButton value="Forgot Password" action="#{myBean.action()}"
            immediate="true"></h:commandButton>
    </h:panelGrid>
</h:form>