diff --git a/upgrade.md b/upgrade.md
index d068be3b..766c4f86 100644
--- a/upgrade.md
+++ b/upgrade.md
@@ -11,3 +11,4 @@ ## Upgrading From 4.0 to 4.1
 - Edit `app/controllers/BaseController.php` change `use Illuminate\Routing\Controllers\Controller;` to `use Illuminate\Routing\Controller;
 `
 - If you are overriding `missingMethod` in your controllers, add $method as the first parameter.
+- If you are registering model observers in a "start" file, move them to the `App::booted` handler.