diff --git a/manuscript/ch9.md b/manuscript/ch9.md
index c5008ea6..57e986e7 100644
--- a/manuscript/ch9.md
+++ b/manuscript/ch9.md
@@ -52,7 +52,7 @@ x = x * 3;
 If we define a function for this multiplying by `3`, that function acts as a mapping (transformer) function:
 
 ```js
-var multipleBy3 = v => v * 3;
+var multiplyBy3 = v => v * 3;
 
 var x = 2, y;