'text search dictionary "unaccent" does not exist' entries in postgres log, supposedly during automatic analyze

I have many such entries in the postgresql main log, ever since upgrading to Postgres 10: 2018-03-28 08:51:00.281 CEST ERROR: text search dictionary "unaccent" does not exist 2018-03-28 08:51:00.281 CEST CONTEXT: automatic analyze of table "dbname.public.periodical" I do use unaccent in many indexes in all tables (by making unaccent immutable (I know it is not the recommended way, but it is so historically)). If I manually run vacuumdb dbname --table periodical or VACUUM periodical or VACUUM ANALYZE periodical, it does not generate such an error (neither on the command line, nor in the log). Does anyone have a tip how I could stop these messages and what their real cause may be? PostgreSQL version: 10.3 (Debian 10.3-1.pgdg80+1)