diff --git a/lib/livebook_web/iframe_endpoint.ex b/lib/livebook_web/iframe_endpoint.ex
index 5866f3687..44ea535ea 100644
--- a/lib/livebook_web/iframe_endpoint.ex
+++ b/lib/livebook_web/iframe_endpoint.ex
@@ -27,10 +27,9 @@ defmodule LivebookWeb.IframeEndpoint do
   """
   @spec port() :: pos_integer()
   def port() do
-    livebook_port = Livebook.Config.port()
     iframe_port = Livebook.Config.iframe_port()
 
-    case livebook_port do
+    case iframe_port do
       0 ->
         try do
           ThousandIsland.listener_info(__MODULE__)