Computed binding parameter in row is undefined v3.0.0-beta1, polymer2

Hi, computed data bindings in rows are not evaluating properly. Parameters (like id) come in as undefined when the _computeRole is evaluated.

<dom-module id="trz-users-view">
  <template>
    <trz-users-model id="model" data="{{users}}" mock></trz-users-model>
    <!-- users.roles = [{id: 0, name: "Admin"}, etc...] -->

    <vaadin-grid class="flex-1" id="material" items="[[users.items]]">
      <vaadin-grid-column-group>
        <template class="header">
        </template>

        <vaadin-grid-selection-column></vaadin-grid-selection-column>
        <vaadin-grid-column  width="50px">
          <template class="header">
            <vaadin-grid-sorter  path="role">
              Role
            </vaadin-grid-sorter>
          </template>
          <template>
            <div class="bodycell">[[_computeRole(item.roleID)]]</div>
          </template>
        </vaadin-grid-column>
      </vaadin-grid-column-group>
    </vaadin-grid>
  </template>
  <script>
    class TRZUsersView extends Polymer.Element {
      static get is() { return 'trz-users-view'; }

      static get properties() {
        return {
          users: {
            type: Object,
            notify: true
          }
        };
      }

      _computeRole(id){
         var temp = this.users.roles.filter(function(val){
            return val.id == id;
          });
          if (temp.length == 0){
            return "";
          } else {
            return temp[0].name;
          }
      }
    }

    window.customElements.define(TRZUsersView.is, TRZUsersView);
  </script>
</dom-module>

vaadin / vaadin-grid

Computed binding parameter in row is undefined v3.0.0-beta1, polymer2 #921