Ember resolving async belongsTo to null

Using the following component in ember-cli (component name if-current-user) the promise for a belongsTo on model.user resolves to null until I save an unrelated model into the store. How do I get it to resolve to the User object associated with the record?

import Ember from 'ember';

export default Ember.Component.extend({
  onUpdate: function() {
    Ember.RSVP.hash({
      user: this.get('user'),
      currentUser: this.get('session.user')
    }).then(function(hash) {
      this.set('isCurrentUser', !!(hash.user && hash.currentUser && hash.user.get('id') === hash.currentUser.get('id'))));
    }.bind(this));
  },
  onUser: function() {
    this.onUpdate();
  }.observes('user').on('init'),
  onCurrentUser: function() {
    this.onUpdate();
  }.observes('session.user').on('init')
});

Model:

import DS from 'ember-data';

export default DS.Model.extend({
  user: DS.belongsTo('user', { async: true }),
  timestamp: DS.attr('number')
});

Template:

{{#if-current-user user=model.user}}
  {{#link-to "route.edit" model}}Edit{{/link-to}}
{{/if-current-user}}

Note that I'm injecting the current session into all components, routes and controllers.