diff --git a/source/chapter2/03_Strings_and_Characters.md b/source/chapter2/03_Strings_and_Characters.md
index 06e3bf2f..21d5eca3 100755
--- a/source/chapter2/03_Strings_and_Characters.md
+++ b/source/chapter2/03_Strings_and_Characters.md
@@ -434,7 +434,7 @@ welcome.removeSubrange(range)
 
 ```swift
 let greeting = "Hello, world!"
-let index = greeting.index(of: ",") ?? greeting.endIndex
+let index = greeting.firstIndex(of: ",") ?? greeting.endIndex
 let beginning = greeting[..<index]
 // beginning 的值为 "Hello"