sieve script with utf-8 not filtering?

[Andreas]

I'm having a problem with the following sieve rule:

(...)
elsif header :contains "List-Id" "Lista de usuários ldap" {
	    fileinto "INBOX.listas.ldapbr";
}

That "usuários" is utf-8 for "usuários". This is the mailing list header:

List-Id: Lista de usuários ldap                                                                                       
        <ldap-l.server.solis.coop.br>                                                                                 

This filter is not working, any idea why? The message just ends up in INBOX,
and the INBOX.listas.ldapbr folder does exist.

I'm using cyrus-2.2.4.

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