validator for an edit profile form with two password fields, but if both are empty.. it should still be valid, either both are empty, or the first has strlen>4 and the second equals it, then it's fine.

However, when both are empty the AgaviEqualsValidator isn't even called because the argument is empty I think.. How can I fix? 

      <validator class="string" required="false">
        <argument>password</argument>
        <parameter name="min">4</parameter>
        <error>The password must be at least 4 characters long</error>
      </validator>

      <validator class="equals">
        <argument>password2</argument>
        <parameter name="value">password</parameter>
        <parameter name="asparam">true</parameter>
        <error>Passwords did not match</error>
      </validator>