OpenApi 3.0 Content-Type

Hello

I have a problem, where after upgrading to openapi 3.0, my endpoint is expecting application/json, but the way it worked before was that it came from consumes/produces, but now it has to be specified in requestBody. I can however not add extra functionality to the code, and by adding a requestBody, it expects me to add a Body element in the method.
I've tried to use a empty requestBody the following ways, but neither of them work:
requestBody:
  content:
    application/json: {}
requestBody:
  content:
    application/json: 
      schema:
        type: object
        nullable: true

Is there another way of doing it, so the only thing that is being added is the content-type, as it was before upgrading?

Thank you