diff --git a/src/guide/essentials/component-basics.md b/src/guide/essentials/component-basics.md
index 042586d3e5..a7342e7898 100644
--- a/src/guide/essentials/component-basics.md
+++ b/src/guide/essentials/component-basics.md
@@ -469,6 +469,7 @@ Something bad happened.
 This can be achieved using Vue's custom `<slot>` element:
 
 ```vue{4}
+<!-- AlertBox.vue -->
 <template>
   <div class="alert-box">
     <strong>This is an Error for Demo Purposes</strong>