public function getCommonChans($nick)
    {
        $nick       = self::extractNick($nick);
        $collator   = $this->connection->getCollator();
        $nick       = $collator->normalizeNick($nick);
        $key        = array_search($nick, $this->nicks);
        if ($key === false) {
            throw new \Erebot\NotFoundException('No such user');
        }

        $results = array();
        foreach ($this->chans as $chan => $users) {
            if (isset($users[$key])) {
                $results[] = $chan;
            }
        }
        return $results;
    }