Create language syntax is not proper in pg_dumpall and not working using pg_upgrade

v9.6

postgres=# CREATE LANGUAGE alt_lang1 HANDLER plpgsql_call_handler;
CREATE LANGUAGE
postgres=# \q

v10 , run pg_upgrade - failing with this error -

pg_restore: creating pg_largeobject_metadata "pg_largeobject_metadata"
pg_restore: creating COMMENT "postgres"
pg_restore: creating SCHEMA "public"
pg_restore: creating COMMENT "SCHEMA "public""
pg_restore: creating PROCEDURAL LANGUAGE "alt_lang1"
pg_restore: [archiver (db)] Error while PROCESSING TOC:
pg_restore: [archiver (db)] Error from TOC entry 560; 2612 16384
PROCEDURAL LANGUAGE alt_lang1 edb
pg_restore: [archiver (db)] could not execute query: ERROR: unsupported
language "alt_lang1"
HINT: The supported languages are listed in the pg_pltemplate system
catalog.
Command was: CREATE OR REPLACE PROCEDURAL LANGUAGE "alt_lang1";

take the cluster dump using pg_dumpall
"
--
-- Name: alt_lang1; Type: PROCEDURAL LANGUAGE; Schema: -; Owner: edb
--

CREATE OR REPLACE PROCEDURAL LANGUAGE alt_lang1;

ALTER PROCEDURAL LANGUAGE alt_lang1 OWNER TO edb;
"

Handler part is missing and due to that it is throwing an error ,if we
try to execute on psql terminal.

--
regards,tushar
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