diff --git a/fastapi/applications.py b/fastapi/applications.py
index 160d66301..204bd46b3 100644
--- a/fastapi/applications.py
+++ b/fastapi/applications.py
@@ -87,7 +87,7 @@ class FastAPI(Starlette):
         ),
         **extra: Any,
     ) -> None:
-        self._debug: bool = debug
+        self.debug = debug
         self.title = title
         self.description = description
         self.version = version
@@ -144,7 +144,7 @@ class FastAPI(Starlette):
         self.user_middleware: List[Middleware] = (
             [] if middleware is None else list(middleware)
         )
-        self.middleware_stack: ASGIApp = self.build_middleware_stack()
+        self.middleware_stack: Union[ASGIApp, None] = None
         self.setup()
 
     def build_middleware_stack(self) -> ASGIApp:
diff --git a/pyproject.toml b/pyproject.toml
index 7b6138d09..696bcda3e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -39,7 +39,7 @@ classifiers = [
     "Topic :: Internet :: WWW/HTTP",
 ]
 dependencies = [
-    "starlette>=0.22.0,<0.24.0",
+    "starlette>=0.24.0,<0.25.0",
     "pydantic >=1.6.2,!=1.7,!=1.7.1,!=1.7.2,!=1.7.3,!=1.8,!=1.8.1,<2.0.0",
 ]
 dynamic = ["version"]