Discriminator in OpenApi 3

In the OpenAPI documentation there is example of using discriminator

components:
  responses:
    sampleObjectResponse:
      content:
        application/json:
          schema:
            oneOf:
              - $ref: '#/components/schemas/Object1'
              - $ref: '#/components/schemas/Object2'
              - $ref: 'sysObject.json#/sysObject'
            discriminator:
              propertyName: objectType
              mapping:
                obj1: '#/components/schemas/Object1'
        obj2: '#/components/schemas/Object2'
                system: 'sysObject.json#/sysObject'

  schemas:
    Object1:
      type: object
      required:
        - objectType
      properties:
        objectType:
          type: string

Unfortunately it work only when objectType is not nested field in Object1. In our project field objectType is nested like this:

  schemas:
    Object1:
      type: object
      properties:
        nextObject:
          type: object
          properties:
             objectType:
             type: string

Is there any solution to point this field out? Something like this..?

  propertyName: nextObject.objectType