Recursive CTE in function problem

Postgres 9.4.1, with these tables:

grpl_collection.collections
id | integer |
name | text |
parent | bigint |
(An adjacency list representing a collections hierarchy)

grpl_collection.collections_copy_map
id | integer |
collection | bigint |
copy | bigint |
(map a copy to the collections it belongs to)

This query correctly answers if a copy is in a collection tree:

select 3006377 in (select copy from
grpl_collection.collections_copy_map where copy=3006377 and collection in
(WITH RECURSIVE
q AS
(
SELECT c.id
FROM grpl_collection.collections c
WHERE name=$$Movies$$
UNION ALL
SELECT cn.id
FROM q
JOIN grpl_collection.collections cn
ON cn.parent = q.id
)
SELECT id
FROM q));

But when I use it as a function it always returns false:

CREATE OR REPLACE FUNCTION grpl_collection.copy_in_collection_name(cpid
bigint, colname text)
RETURNS boolean
LANGUAGE plpgsql
AS $function$
BEGIN
RETURN cpid in (select copy from
grpl_collection.collections_copy_map where copy=cpid and collection in
(WITH RECURSIVE
q AS
(
SELECT c.id
FROM grpl_collection.collections c
WHERE name=$$colname$$
UNION
SELECT cn.id
FROM q
JOIN grpl_collection.collections cn
ON cn.parent = q.id
)
SELECT id FROM q ));
END;
$function$

What am I missing?