Ember model stays in "inFlight" state after 409 response from server using JSON API

I am in the process of upgrading Ember and Ember Data to 1.13.x. I switched to using the new JSON API adapter/serializer and also changed the server response to conform the JSON API format. However I am having problem with an error handling scenario. A model gets properly updated when following the happy path but when the update needs to fail because say optimistic lock detects simultaneous updates then I have the model stuck in "inFlight" state.

This is an example request:

{
  data: {
    id: "1",
    type: "books",
    attributes: {
      name: "New Book Name",
      version: 1
    }
  }
}

The server finds out that the current version is greater than 1 and rejects the update with 409 HTTP status code and the response is:

{
  errors: [{
    code: "2",
    detail: "Simultaneous changes.",
    source: { 
      pointer: "data" 
    },
    status: "409"
  }]
}

The problem is that after the server response my model is in "root.loaded.updated.inFlight" state. Even after calling model.rollbackAttributes() the state doesn't change.

Is this a problem in the server response JSON? Is this a bug in Ember Data?

Feedback is appreciated.