OAuth with ldap user not working

Gitlab-CE version: 7.10.1 d5c71c83

I'm trying to create an access token for an ldap user. For normal db users the call to /oauth/token works with the parameters according to the documentation

{
  "grant_type"    : "password",
  "username"      : "user@example.com",
  "password"      : "sekret"
}

But when I do the same call with my ldap user I get a 401

{
    "error": "invalid_grant",
    "error_description": "The provided authorization grant is invalid, expired, revoked, does not match the redirection URI used in the authorization request, or was issued to another client."
}

In the logs apears a message

Started POST "/gitlab/oauth/token" for ***.***.***.*** at 2015-05-12 10:53:32 +0200

Processing by Doorkeeper::TokensController#create as HTML

Parameters: {"grant_type"=>"password", "username"=>"myurl", "password"=>"[FILTERED]"}

Completed 401 Unauthorized in 321ms