Domain Implicit Casting Trouble

I came across the following problem when migrating from 7.3.4 to 7.4b4.
Query #4 does not fail under version 7.3.4. But it does under version
7.4b4. It seems that in some situations the implicit cast fails. It
would not be a problem if I had the opportunity to manually cast these
queries. But I don't. I am using a client package (Hibernate) which
generates statements automatically based on an O/R mapping.

CREATE DOMAIN foo_varchardomain AS varchar(10);

CREATE DOMAIN foo_intdomain AS int4;

CREATE TABLE foo_table (i foo_intdomain, c foo_varchardomain);

INSERT INTO foo_table VALUES (1, 'x');

SELECT * FROM foo_table WHERE i = '1'::text;

SELECT * FROM foo_table WHERE i::int4 = '1'; -- query #1 ok

SELECT * FROM foo_table WHERE i = 1; -- query #2 ok

SELECT * FROM foo_table WHERE c = 'x'; -- query #3 ok

SELECT * FROM foo_table WHERE i = '1'; -- query #4 ERROR
ERROR: operator is not unique: foo_intdomain = "unknown"
HINT: Could not choose a best candidate operator. You may need to add
explicit type casts.

TIA
David