Vanilla API User Not Found

I got the api running and tried querying a category id which works ok..

http://forum.mysite.com/api/category/2

trying on users end point gives me a not found result

http://forum.mysite.com/api/users/5

even though I have a user with that id

{"Code":404,"Exception":"User not found.","Class":"Gdn_UserException"}

This one works btw listing all users:

http://forum.mysite.com/api/users/