non-covered NEST/INDEX JOIN gives wrong results

insert into default values("a_12345",{ "_id": "a_12345", "_type": "service" });

insert into default values("b_12345", { "_id": "b_12345", "parent": "a_12345", "data": { "a": "b", "c": "d" } });

insert into default values("b_12346", { "_id": "b_12346", "parent": "a_12345", "data": { "6": "3", "d": "f" } });

create primary index on default;

CREATE INDEX idx_parent ON default( parent );

SELECT * FROM default a NEST default b ON KEY b.parent FOR a;

gives no results.  Should return 1 row