add a value to an ENUM type - Mailing list pgsql-general

I have an enum type
CREATE TYPE shapeName AS ENUM('rectangle','circle');

now I need another value: 'square'

the pg_type.oid of 'shapename is 16458

It works, but Is it safe to use this?
insert into pg_enum (enumtypid,enumlabel) VALUES('16458','square');

thank you
Edoardo