diff --git a/exercises-9-9.md b/exercises-9-9.md
index 22202c5575b7ebf8485fe6490587cd39fdfe65f4..65a3865cfa83f6ebb7663d12f297a2c07207f0f3 100644
--- a/exercises-9-9.md
+++ b/exercises-9-9.md
@@ -1,3 +1,4 @@
+```swift
 struct Stack<Element> {
       var items = [Element]()
       mutating func push(_ item: Element) {
@@ -175,3 +176,4 @@ class Person {
 
 //=====================================================================
 
+```