Action response format

I have an action which should return JSON request.

I’ve added accept :json to my action, and format :json to my corresponding view.

But during json request, hanami fails with error because of no view found.

After I specified format inside call method of the action, it started working:

def call(params)
  self.format = :json

So I was wondering if it is correct behaviour and why do I need to specify accept :json in this case?