OpenAPI generator Swift 4 enum issue

example.yaml

openapi: "3.0.0"
info:
  version: 1.0.0
  title: Swagger Petstore
  license:
    name: MIT
servers:
  - url: http://petstore.swagger.io/v1
paths:
  /pets:
    post:
      description: Creates a new pet in the store.  Duplicates are allowed
      operationId: addPet
      requestBody:
        description: Pet to add to the store
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/NewPet'

components:
  schemas:
    NewPet:
      required:
        - name  
      properties:
        animal:
          type: string
          enum: 
          - dog
          - cat
          default: cat