diff --git a/recognization/code/transport.py b/recognization/code/transport.py
index 292a95e..66e94a1 100644
--- a/recognization/code/transport.py
+++ b/recognization/code/transport.py
@@ -116,41 +116,37 @@ class BodyLimit:
         if scope.get("type") != "http":
             await self.app(scope, receive, send)
             return
-        seen = 0
-        blocked = False
+        class TooLarge(Exception):
+            pass
 
+        seen = 0
         async def limited() -> Dict[str, Any]:
-            nonlocal seen, blocked
-            if blocked:
-                return {"type": "http.request", "body": b"", "more_body": False}
+            nonlocal seen
             message = await receive()
             if message.get("type") != "http.request":
                 return message
             body = message.get("body") or b""
             seen += len(body)
             if seen > self.max_bytes:
-                blocked = True
-                await send(
-                    {
-                        "type": "http.response.start",
-                        "status": 413,
-                        "headers": [(b"content-type", b"application/json")],
-                    }
-                )
-                await send(
-                    {
-                        "type": "http.response.body",
-                        "body": b'{"error":{"code":"PAYLOAD_TOO_LARGE","message":"request body too large"}}',
-                    }
-                )
-                return {"type": "http.request", "body": b"", "more_body": False}
+                raise TooLarge
             return message
 
         try:
             await self.app(scope, limited, send)
-        except RuntimeError:
-            if not blocked:
-                raise
+        except TooLarge:
+            await send(
+                {
+                    "type": "http.response.start",
+                    "status": 413,
+                    "headers": [(b"content-type", b"application/json")],
+                }
+            )
+            await send(
+                {
+                    "type": "http.response.body",
+                    "body": b'{"error":{"code":"PAYLOAD_TOO_LARGE","message":"request body too large"}}',
+                }
+            )
 
 
 SERVICE_TYPE = "_dorayaki._tcp"