Use this method to restore the old Ember Data behavior where properties with missing keys in the payload gets cleared.

gistfile1.js

App.ApplicationSerializer = DS.RESTSerializer.extend({

  normalizeAttributes: function(type, hash) {
    this._super(type, hash);
  
    type.eachAttribute(function(key) {
      if (!hash.hasOwnProperty(key)) {
        hash[key] = null;
      }
    }, this);
  }

});