private function getObjectAceIndex(AclInterface $acl, $role)
    {
        $objectAces = $acl->getObjectAces();
        /* @var $ace AuditableEntryInterface */
        foreach ($objectAces as $index => $ace) {
            $securityIdentity = $ace->getSecurityIdentity();
            if ($securityIdentity instanceof RoleSecurityIdentity) {
                if ($securityIdentity->getRole() == $role) {
                    return $index;
                }
            }
        }

        return false;
    }