Error when submitting user registration form in Portal

[baddlan]

Request:

POST /registrations
{
  "data": {
    "firstName": "Sam",
    "lastName": "Fergeson"
  },
  "version": 1,
  "username": "sam@individual.ds",
  "password": "sam",
  "identity": "Individual"
}

Response (500 Server Error):
Attempted to call an undefined method named "setPossessor" of class "AppBundle\Entity\User".