diff --git a/lib/elixir/pages/mix-and-otp/docs-tests-and-with.md b/lib/elixir/pages/mix-and-otp/docs-tests-and-with.md
index 729f3ef52e8..f9c97c50330 100644
--- a/lib/elixir/pages/mix-and-otp/docs-tests-and-with.md
+++ b/lib/elixir/pages/mix-and-otp/docs-tests-and-with.md
@@ -371,7 +371,7 @@ defmodule KVServerTest do
 
   setup do
     opts = [:binary, packet: :line, active: false]
-    {:ok, socket} = :gen_tcp.connect('localhost', 4040, opts)
+    {:ok, socket} = :gen_tcp.connect(~c"localhost", 4040, opts)
     %{socket: socket}
   end