domain over enum problem

CREATE TYPE zzz_enum AS ENUM ('A', 'B', 'C');
CREATE TABLE zzz_test1 (z zzz_enum);
SELECT * FROM zzz_test1 WHERE z = 'A';

That works.  But:

CREATE DOMAIN zzz AS zzz_enum DEFAULT 'A';
CREATE TABLE zzz_test2 (z zzz);
SELECT * FROM zzz_test2 WHERE z = 'A';
ERROR:  42883: operator does not exist: zzz = unknown