diff --git a/README.md b/README.md
index edab67c45..4912fb8c7 100644
--- a/README.md
+++ b/README.md
@@ -62,7 +62,7 @@ export class AppComponent {
 
   constructor() {
     const itemCollection = collection(this.firestore, 'items');
-    this.item$ = collectionData(itemCollection);
+    this.item$ = collectionData(itemCollection) as Observable<Item[]>;
   }
 }
 ```