search_path for replica-mode

There is a trigger in the database

SET search_path TO "$user", public;

CREATE OR REPLACE FUNCTION art__a_iu_func()
BEGIN
  INSERT INTO table_z...   --»table_z« is in schema public
END;

CREATE OR REPLACE TRIGGER art__a_iu
    AFTER INSERT OR UPDATE OF ak_nr
    ON art
    FOR EACH ROW
    EXECUTE FUNCTION art__a_iu_func();

In a regular trigger, it works great!
But, if I announce it, as:

ALTER TABLE art ENABLE REPLICA TRIGGER art__a_iu;
then I get an error:

FEHLER:  Relation »table_z« existiert nicht bei Zeichen xxx
ANFRAGE:  INSERT INTO table_z...

why does'nt work the search_path for replica-mode?
is it made specifically or is it a bug?
How else can I set the search_path for replica-mode?