diff --git a/sanic/app.py b/sanic/app.py
index bb3b4b0e..d80bd242 100644
--- a/sanic/app.py
+++ b/sanic/app.py
@@ -78,6 +78,7 @@ class Sanic(BaseSanic):
     """
 
     __fake_slots__ = (
+        "_asgi_app",
         "_app_registry",
         "_asgi_client",
         "_blueprint_order",