Error: Unexpected value 'undefined' imported by the module

Ionic Framework ionic-v3
1

Hello,

What can be cause of Error: Unexpected value 'undefined' imported by the module, if I have import { NgCalendarModule } from 'ionic2-calendar'; in app.module.ts:

  imports: [
    BrowserModule,
    HttpModule,
    HttpClientModule,
    NgCalendarModule,
    IonicModule.forRoot(MyApp),
    IonicStorageModule.forRoot()
  ],

Error disappears if I remove import { NgCalendarModule } from 'ionic2-calendar'; and then save. if I add import again, everything works. Error appears with undefined saving, and eliminated same way as described