Bug in API behavior with lists

[dirs]

I'm using "lists" as a way to look for geo related users. So for get
lists of a user I use:
http://api.twitter.com/1/USER_ID/lists/memberships.xml

I know that user_id insted of screen_name are not documented but I
expected that it works and it works!

So I'm trying too to get others users from the lists that my first
user are...

http://api.twitter.com/1/user/list_id/members.format

But here I can't get API to work with user_id and I really don't want
to use screen_name.

http://api.twitter.com/1/45232963/1505300/members.xml
I think that it might work

It seems like a bug. Twitter might accept IDs...