diff --git a/maths/factorial.js b/maths/factorial.js
index 7130de52c..febc5c0c4 100644
--- a/maths/factorial.js
+++ b/maths/factorial.js
@@ -48,6 +48,6 @@ function calcFactorial (num) {
 }
 
 // Run `factorial` Function to find average of a list of numbers.
-// global alert, prompt
+/* global alert, prompt */
 var num = prompt('Enter a number: ')
 alert(calcFactorial(num))