Warning: sieve: file storage: Active sieve script symlink is broken: Invalid/unknown path to storage

dovecot version: 2.2.16 (3d8a054a93a9)

sieve configuration: plugin { sieve = ~/.dovecot.sieve sieve_dir = ~/sieve }

For each of the users, ~/.dovecot.sieve is a symlink to ~/sieve/roundcube.sieve

Until yesterday, everything was working find. But starting from yesterday's update, the log is filling up with messages like: Mar 16 19:12:32 cs12986 dovecot: lda(postmaster@contoso.com <postmaster@euro-contact.ru>): Warning: sieve: file storage: Active sieve script symlink /home/virtualmail/contoso.com/it/.dovecot.sieve <http://euct.ru/it/.dovecot.sieve> is broken: Invalid/unknown path to storage (points to /home/virtualmail/contoso.com/it/sieve <http://euct.ru/it/sieve>).

Nothing was changed in the config files.

What might have gone wrong?