orphanRemoval does not work with oneToOne: Duplicate entry Error

/*
Error:
SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1' for key 'UNIQ_9D8DDB05579B502F'
*/

/*
Contact:
  type: entity
  table: contact
  fields:
    _id:
      id: true
      type: integer
      unsigned: true
      nullable: false
      generator:
        strategy: AUTO
      column: id
  oneToOne:
    _standingData:
      targetEntity: StandingData
      mappedBy: _contact
      cascade: ["persist", "merge", "remove"] 
      orphanRemoval: true
*/

class Contact
{
    private $_id;
    private $_standingData;

    public function newStandingData(StandingData $sd)
    {
        $this->_standingData = $sd;
        $sd->setContact($this);
    }
}

/*
StandingData:
  type: entity
  table: standing_data
  fields:
    _id:
      id: true
      type: integer
      unsigned: true
      nullable: false
      generator:
        strategy: AUTO
      column: id
  oneToOne:
    _contact:
      targetEntity: Contact
      inversedBy: _standingData
      joinColumns:
        contact_id:
          referencedColumnName: id
          onDelete: cascade
*/

class StandingData
{
    private $_id;
    private $_contact;

    public function setContact(Contact $c)
    {
        $this->_contact = $c;
    }
}

// Create new Contact
$contact = new Contact();
$contact->newStandingData(new \StandingData());
$em->persist($contact);
$em->flush();

// Try to change StandingData
$contact->newStandingData(new \StandingData());
$em->flush();