disabling File>Delete

System

I´m trying to disable File>delete option for the Master role.

I´ve modified the ui_custom.xml file that way:
<iwov-delete>
<link id="iw.ccpro.file_menu.delete.link" />
</iwov-delete>
<link id="iw.ccpro.file_menu.delete.link"
refid="_iw.ccpro.delete.link"
operationID="iw.ccpro.file_menu.delete.op"
target="_hidden"/>
</link>

and in the roles_custom.xml if modified in the master_role the following:

<operation id="iw.ccpro.file_menu.delete.op" isPermitted="false" />

But when loggin as master I can see File > delete.

Should I modify anything else?

Thanks in advanced!!!!