diff --git a/code/ch01/ex01-babel-setup/src/example.js b/code/ch01/ex01-babel-setup/src/example.js
index 2351443..37bca8b 100644
--- a/code/ch01/ex01-babel-setup/src/example.js
+++ b/code/ch01/ex01-babel-setup/src/example.js
@@ -1,3 +1,3 @@
-var double = value => value * 2
+let double = value => value * 2
 console.log(double(3))
 // <- 6