diff --git a/03_Day_Setting_Up/03_setting_up_boilerplate/src/index.js b/03_Day_Setting_Up/03_setting_up_boilerplate/src/index.js
index 8d7e972..24928b7 100644
--- a/03_Day_Setting_Up/03_setting_up_boilerplate/src/index.js
+++ b/03_Day_Setting_Up/03_setting_up_boilerplate/src/index.js
@@ -64,7 +64,7 @@ const personAge = (
 
 // JSX element, main
 const techs = ['HTML', 'CSS', 'JavaScript']
-const techsFormatted = techs.map((tech) => <li>{tech}</li>)
+const techsFormatted = techs.map((tech) => <li key={tech}>{tech}</li>)
 
 const user = (
   <div>