Getting error when upgrading from ember-data 2.5 to 2.8

• ember-data@2.5.3 to ember-data@2.9.0
• ember@2.4.1 to ember@2.8.3

The following worked fine before the update, it appears that ember-data is causing the issue.

Getting the following error: Uncaught TypeError: Cannot read property 'eachAttribute' of undefined

I am reloading a model this.modelFor('admin').get('ssoApplicationSubscriptions').reload();

When it starts executing the eachAttribute loop I get the error. Interestingly the constructor is undefined at this point.

Here are the model definitions

// Organisation
export default DS.Model.extend({
  name: attr('string')
});

// Institution Organisation
export default Organisation.extend({
  ssoApplicationSubscriptions: hasMany('sso-application-subscription', { polymorphic: true })
});

I am using the JSONAPIAdapter/Serializer.