Refs in responses don't seem to work

[mgm1313]

paths:
  /healthz:
    get:
      operationId: healthCheck
      tags:
        - system
      summary: Health check endpoint
      description: Check if the API is up and running
      responses:
        "200":
          description: OK
          content:
            application/json:
              schema:
                type: object
                properties:
                  status:
                    type: string
                    example: "OK"
        "500":
          $ref: "./responses.yaml#/$defs/InternalServerError"

responses.yaml

$schema: https://json-schema.org/draft/2020-12/schema

$defs:
  InternalServerError:
    description: Internal Server Error

This syntax causes the issue described in #100