Ember Assertion Failed: You need to pass a model name to the store's modelFor method

Ember 2.4.0

Ember Data 2.4.0

so I'm trying to return an object "api-user-list" that is comprised of two models, a pager object named "pager" and a collection of users called "api-user"

pager model

import DS from 'ember-data';
import { belongsTo } from 'ember-data/relationships';

export default DS.Model.extend({
    PageSize: DS.attr(),
    SkipPages: DS.attr(),
    SearchStr: DS.attr(),
    TotalCount: DS.attr(),
    PageCount: DS.attr()
});

apiUser Model

import DS from 'ember-data';

export default DS.Model.extend({
    UserName: DS.attr(),
    First: DS.attr(),
    Last: DS.attr(),
    Bio: DS.attr(),
    OrgId: DS.attr(),
    CreatedAt: DS.attr(),
    DeActivatedAt: DS.attr(),
    PasswordSetAt: DS.attr(),
    PhoneNumber: DS.attr()
});

the complex model "api-user-list"

import DS from 'ember-data';
import Model from 'ember-data/model';
import { belongsTo, hasMany } from 'ember-data/relationships';

export default Model.extend({
    pager: belongsTo('pager', { async: false }),
    apiUser: hasMany('api-user', { async: false })
});

returned JSON

{
  "apiUserList": {
    "id": 1,
    "pager": {
      "id": 1,
      "PageSize": 2,
      "SkipPages": 0,
      "SearchStr": null,
      "TotalRecords": 2,
      "TotalPages": 1
    },
    "apiUser": [
      {
        "id": 3,
        "UserName": "dude 2",
        "First": "Allen",
        "Last": "Smith",
        "Bio": null,
        "OrgId": 0,
        "CreatedAt": "2016-07-14T19:27:20.757",
        "DeActivatedAt": null,
        "PasswordSetAt": "2016-07-14T19:32:38.34",
        "PhoneNumber": null
      },
      {
        "id": 2,
        "UserName": "dummyUser",
        "First": "dude",
        "Last": "dude last name",
        "Bio": null,
        "OrgId": null,
        "CreatedAt": "2016-07-08T10:53:35.017",
        "DeActivatedAt": null,
        "PasswordSetAt": "2016-07-27T16:07:35.073",
        "PhoneNumber": null
      }
    ]
  }
}

it looks like the correct model is being returned but get an error when the "pager" is trying to be pushed into the store:

Assertion Failed: You need to pass a model name to the store's modelFor method

in the debugger I can see that I enter

function deserializeRecordId()

but when it tries to read the id.type variable it's always 'undefined'. Does anyone have an idea where I am missed something?