diff --git a/aio/content/examples/toh-pt4/src/app/heroes/heroes.component.ts b/aio/content/examples/toh-pt4/src/app/heroes/heroes.component.ts
index 020cd6c8e4..bd29c51058 100644
--- a/aio/content/examples/toh-pt4/src/app/heroes/heroes.component.ts
+++ b/aio/content/examples/toh-pt4/src/app/heroes/heroes.component.ts
@@ -15,10 +15,10 @@ import { MessageService } from '../message.service';
 })
 export class HeroesComponent implements OnInit {
 
-  selectedHero: Hero;
+  selectedHero?: Hero;
 
   // #docregion heroes
-  heroes: Hero[];
+  heroes: Hero[] = [];
   // #enddocregion heroes
 
   constructor(private heroService: HeroService, private messageService: MessageService) { }