Ember destroyRecord on polymorphic record calls the wrong route

I have a polymorphic record type in my ember application. Posts has a polymorphic association called response, which can be a few kinds of response.

// post.js
import DS from 'ember-data';

export default DS.Model.extend({
  ...
  responses: DS.hasMany('response', { polymorphic: true })
});

The response model is the basis for all the other types.

// response.js
import DS from 'ember-data';

export default DS.Model.extend({
  post: DS.belongsTo('post'),
  message: DS.attr('string')
});

For example, a comment inherits from response.

// comment.js
import Response from '../models/response';

export default Response.extend();

This works perfectly for loading models using ember-data. It correctly connects to /responses on the Rails server for all types of responses.

However when I try to delete a record using record.destroyRecord() it sends the delete to /comments on the server, instead of /responses. Because this is a polymorphic record there is no comments route on the server.

Is there some other part of ember-data where I can indicate the record deletion should be polymorphic?