Is Accept application/json as default possible for importing OAS3?

My question:
I imported OAS3 spec and got a Postman Collection.
Now I found that all requests have automatically Accept /.
Which the application does not accept, it needs to have Accept application/json in the request.
Now is it possible to tell Postman to use Accept application/json for all requests for the import of an OAS3 document ?
Or can that be scripted to change it for all requests after import ?

How I found the problem:
Import of OpenAPI specification.