PHP Missing NameSpace When OneOf Reference Used

Codegen 3.0.20.  Have an object defined as below. Swagger generates a OneOfPaymentResponseDataPaymentMethod and PaymentResponseData model files. 

In the PaymentResponseData class $swaggerTypes property the Namespace is not applied to payment_method. I have to manually add the Namespace here.

Not the author of this but trying to understand what is causing this. Thanks.

    protected static $swaggerTypes = [
        'payment_type' => '\NameSpace\Model\PaymentType',
'payment_method' => 'OneOfPaymentResponseDataPaymentMethod',
'amount' => 'double',
'billing_first_name' => 'string',
'billing_last_name' => 'string',
'billing_phone' => 'string',
'billing_address' => '\NameSpace\Model\Address',
'notes' => 'string',
'error_message' => 'string'    ];

PaymentResponseData:
  type: object
  required:
    - paymentType
    - paymentMethod
    - amount
    - billingFirstName
    - billingLastName
    - billingPhone
    - billingAddress
    - notes
  properties:
    paymentType:
      $ref: "#/components/schemas/PaymentType"
    paymentMethod:
      oneOf:
        - $ref: "#/components/schemas/CreditCardResponse"
        - $ref: "#/components/schemas/CreditCardTokenResponse"
    amount:
      type: number
      format: double
      example: 550.12
    billingFirstName:
      type: string
      example: John
    billingLastName:
      type: string
      example: Smith
    billingPhone:
      type: string
      example: 800-343-2891
    billingAddress:
      $ref: "#/components/schemas/Address"
    notes:
      type: string
    errorMessage:
      type: string
      nullable: true