public function validatePayload($packedPayload)
    {
        $messageType = $this->message->getMessageType();
        $maxLength   = $this->getPayloadMaxLength();

        if (strlen($packedPayload) > $maxLength) {
            throw new MalformedNotificationException(
                sprintf(
                    "The maximum size allowed for '%s' notification payload is %d bytes",
                    $messageType,
                    $maxLength
                )
            );
        }
    }