I'm trying to add another class to the wrapwrap div located in fronend_layout. But the following code doesn't seem to work in Odoo 11 Community.

Anyone have a fix for this. I know the xpath is correct beucase I can add different attributes and they work. But class just won't work at all.

<template id="sws_nucleus" inherit_id="portal.frontend_layout" name="Add Nucleus">
    <xpath expr="//div[@id='wrapwrap']" position="attributes">
        <attribute name="class">nucleus</attribute>
    </xpath>
</template>