[Dovecot] [LMTP] sieve filter does not drop privilleges?

[Kamil Jońca]

I have (user) sieve filter in my home dir. 
This filter uses  "vnd.dovecot.filter" extension to call some shell
scripts. These scrips creates some temporary files.
Strange thing:
whent sieve is called via dovecot-lda - these files are created by user
"kjonca"
when sieve is called via lmtp - these files are created by root.
Is there any way to drop privilleges where lmtp passing messages to
sieve?
KJ

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