ngbTabset templateRef issue

Usage

<ngb-tabset>
  <ngb-tab title="Simple">
    <ng-template>
      <p>Raw deni....erican apparel, butcher voluptate nisi qui.</p>
    </ng-template>
  </ngb-tab>
</ngb-tabset>

Get error:

core.es5.js:1084 ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'templateRef' of undefined
TypeError: Cannot read property 'templateRef' of undefined
    at Object.View_NgbTabset_4.co [as updateDirectives] (NgbTabset.html:20)

it’s the line:

<ng-template [ngTemplateOutlet]="tab.contentTpl.templateRef"></ng-template>

Packages versions
"@ng-bootstrap/ng-bootstrap": "1.0.0-alpha.25"
"@angular/x: 4.0.1