Why this aggregate function cannot be converted with pg_upgrade from PostgreSQL 9.5 to PG 14.3?

I am trying to port old PostgreSQL v9.5 database (or family of databases) to PostgreSQL v14.3, with pg_upgrade utility. After many hassles with old v9.5 binaries, source files (had to be recompiled to be runnable in the much newer OS and libraries, fedora 24->fedora 36), adding several extensions from postgresql-contrib and from GIT; I finally got pg_upgrade --check completed saying the databases are compatible. postgres$ postgresql-setup --initdb postgres$ pg_upgrade --check -b postgresql-9.5.7/bin -B /usr/bin -d data.old -D data Performing Consistency Checks ----------------------------- Checking cluster versions ok Checking database user is the install user ok Checking database connection settings ok Checking for prepared transactions ok Checking for system-defined composite types in user tables ok Checking for reg* data types in user tables ok Checking for contrib/isn with bigint-passing mismatch ok Checking for user-defined encoding conversions ok Checking for user-defined postfix operators ok Checking for tables WITH OIDS ok Checking for invalid "sql_identifier" user columns ok Checking for invalid "unknown" user columns ok Checking for hash indexes ok Checking for roles starting with "pg_" ok Checking for presence of required libraries ok Checking database user is the install user ok Checking for prepared transactions ok Checking for new cluster tablespace directories ok *Clusters are compatible* But then running pg_upgrade without --check it stops here: $ tail -12 pg_upgrade_dump_308771.log pg_restore: creating AGGREGATE "foobardb.ads("anyelement")" pg_restore: while PROCESSING TOC: pg_restore: from TOC entry 1800; 1255 514033 AGGREGATE ads("anyelement") dbuser pg_restore: error: could not execute query: ERROR: function array_append(anyarray, anyelement) does not exist Command was: CREATE AGGREGATE "foobar"."ads"("anyelement") ( SFUNC = "array_append", STYPE = "anyarray", INITCOND = '{}', FINALFUNC = "foobardb"."array_sort_unique" ); The aggregate function file which has created the aggregate: ads.sql, which have function array_sort_unique(ANYARRAY), which takes any array, finds unique values in it and orders them. And ads(ANYELEMENT) aggregate function, which can be used to aggregate items in GROUP BY queries and returning an array of unique items ordered. -- Array_agg + unique/Distinct 'sort' CREATE OR REPLACE FUNCTION array_sort_unique (ANYARRAY) RETURNS ANYARRAY LANGUAGE SQL AS $body$ SELECT ARRAY( SELECT DISTINCT $1[s.i] FROM generate_series(array_lower($1,1), array_upper($1,1)) AS s(i) ORDER BY 1 ); $body$; --https://www.postgresql.org/docs/9.5/xaggr.html CREATE aggregate ads (ANYELEMENT) --RETURNS ANYARRAY ( sfunc = array_append, stype = anyarray, initcond = '{}', finalfunc = array_sort_unique ) pg_upgrade seems to claim, there is no array_append(anyarray, anyelement) function, but there is: PGSQL: array_append(anyarray, anyelement) And it was working without problems in PGSQL v9.5 **Any idea, why there is an error and how to fix it?** Why PGSQL v9.5 is happy, but porting to PGSQL 14.3 fails? Edit: Is it because in newer PGSQL *array_append(anyarray, anyelement)* is now *array_append(anycompatiblearray, anycompatible)*? I guess. PGSQL type system - polymorphic types **How to tell pg_upgrade to handle with that? Or how to tackle that problem?**