diff --git a/getting-started/mix-otp/supervisor-and-application.markdown b/getting-started/mix-otp/supervisor-and-application.markdown
index 666c78311..e5fc7a728 100644
--- a/getting-started/mix-otp/supervisor-and-application.markdown
+++ b/getting-started/mix-otp/supervisor-and-application.markdown
@@ -236,6 +236,7 @@ Since we have specified `KV` as the module callback, let's change the `KV` modul
 defmodule KV do
   use Application
 
+  @impl true
   def start(_type, _args) do
     # Although we don't use the supervisor name below directly,
     # it can be useful when debugging or introspecting the system.