Grant_type=password for LDAP user


In my GitLab installation I use LDAP to authenticate AD users.
I’m trying to use OAuth with the grant_type=password type for a one page webapp I host on the same server to allow users quick access to their info.
When I’m testing oauth/token with a GitLab “native” user I get the token back.
If I’m tying the same with an LDAP user (username=380157916B8AA7E7A87FA9), I get {"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."}

Is it impossible to use this OAuth method for LDAP users?