We have own layout for MessageBox component, which covers most of modal windows in our application.
We are using a Messagebox.setTemplate("/WEB-INF/zk/unsecure/messagebox.zul"); mehod in AppInit class, defined in zk.xml as

    <listener>
        <description>ZK App init</description>
        <listener-class&gt;{our_package}.AppInit</listener-class&gt;
    </listener>

We also have own layout for error-page, defined in zk.xml

    <error-page>
        <exception-type>java.lang.Throwable</exception-type>
        <location>/WEB-INF/zk/unsecure/error.zul</location>
    </error-page>

All of this features works well

Problem is:
We defined a constraint on a component in ZUL file, like maxsize on FileUpload

<fileupload id="fileUpload" upload="true,maxsize=10" label="${llabels.fill_from_excel}" sclass="btn"/>

When I try tu upload a file with bigger size than 10kb, some modal window appear, but with a wrong (maybe some default) layout. It looks like messagebox layout before our changes.
I was searching for a while, if I can set a template for another component, but I don't know, for what component.
I am not able to reproduce this modal window by simple button with onClick event.

        <button label="Cause Alert" onClick='alert("Alert test");'/>

This button shows right modal window, because it uses a Messagebox component. (screenshot-1)

But when i upload large file to my FileUpload, modal window is wrong and has no z-messagebox sclass (screenshot-2)

Please help me with some advice