diff --git a/docs/guide/expanding.md b/docs/guide/expanding.md
index d5856a0d7c..8ca11daaf9 100644
--- a/docs/guide/expanding.md
+++ b/docs/guide/expanding.md
@@ -49,10 +49,10 @@ type Person = {
   id: number
   name: string
   age: number
-  children: Person[]
+  children?: Person[] | undefined
 }
 
-const data: Person =  [
+const data: Person[] =  [
   { id: 1, 
   name: 'John', 
   age: 30,