[Dovecot] Sieve vacation with russian subject

[Nikita Koshikov]

Hello list,

I have noticed that sieve vacation action breaks some non-english letters in the subject.
I tested with russian language, if subject contains letters from specific diapason russian alphabet, the message received with unreadable subject, but text in the body with the same letters looks ok.
Here is example of full subject header, it contains russian alphabet:
Subject: абвгде�?жзийклмноп�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?

Maybe this headers will be usefull:
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit

.dovecot.sieve file looks correct, here is it:
require ["vacation"];
# rule:[test]
if anyof (true)
{
        vacation :days 1 :addresses ["user at domain.com"] :subject "абвгдеёжзийклмнопрстуфхцчшщъыьэюя" text:
Тестовое русское сообщение(Test russian message).
;
}

I'm running dovecot-1.1.16 with dovecot-sieve-1.1.6 and managesieve-0.10.6.

Please tell, is it possible to fix this ?