diff --git a/src/ziplineio/app.py b/src/ziplineio/app.py
index 2eefeac..35020d8 100644
--- a/src/ziplineio/app.py
+++ b/src/ziplineio/app.py
@@ -9,7 +9,7 @@
 from ziplineio import settings
 from ziplineio.handler import Handler
 from ziplineio.request import Request
-from ziplineio.response import NotFoundResponse, format_response
+from ziplineio.response import Response, NotFoundResponse, format_response
 from ziplineio.router import Router
 from ziplineio.static import staticfiles
 from ziplineio.utils import call_handler, parse_scope
@@ -103,8 +103,9 @@ async def _get_and_call_handler(
             return res
 
         if self._router._not_found_handler:
-            body = await call_handler(self._router._not_found_handler, req)
-            return NotFoundResponse(body)
+            response = await call_handler(self._router._not_found_handler, req)
+            headers = isinstance(response, Response) and response._headers or {}
+            return NotFoundResponse(response, headers)
 
         return NotFoundHttpException()
 
@@ -131,42 +132,3 @@ async def uvicorn_handler(scope: dict, receive: Any, send: Any) -> None:
                 )
 
         return uvicorn_handler
-
-
-app = App()
-
-
-async def logging_middleware(req: Request) -> Tuple[Request, dict]:
-    print(f"Received request: {req.method} {req.path}")
-    # Pass along request and an empty context (no modifications)
-    return req, {}
-
-
-async def auth_middleware(req: Request) -> Tuple[Request, dict]:
-    # Modify the context with some auth information
-    return req, {"auth": "Unauthorized"}
-
-
-class LoggingService:
-    def log(self, message: str) -> None:
-        print(f"Logging: {message}")
-
-
-@app.get("/")
-@inject(LoggingService)
-@middleware([logging_middleware, auth_middleware])
-async def handler(req: Request, ctx: dict, LoggingService: LoggingService) -> dict:
-    res = {"message": "Hello, world!"}
-
-    # Use the injected LoggingService
-    LoggingService.log(f"Params: {req.query_params.get('bar')}")
-
-    return {**res, **ctx}
-
-
-@app.get("/foo/:bar")
-async def handler2(req: Request) -> dict:
-    bar = req.path_params.get("bar")
-    res = {"message": f"Hello, {bar}!"}
-
-    return res
diff --git a/src/ziplineio/response.py b/src/ziplineio/response.py
index 73bc786..073080e 100644
--- a/src/ziplineio/response.py
+++ b/src/ziplineio/response.py
@@ -55,8 +55,8 @@ def __init__(self, body: str):
 
 
 class NotFoundResponse(Response):
-    def __init__(self, body: str):
-        super().__init__(404, {}, body)
+    def __init__(self, body: str, headers: Dict[str, str] = {}):
+        super().__init__(404, headers, body)
 
 
 def format_headers(headers: Dict[str, str] | None) -> List[Tuple[bytes, bytes]]:
diff --git a/test/test_e2e.py b/test/test_e2e.py
index 9a2ea9a..b6ef4fb 100644
--- a/test/test_e2e.py
+++ b/test/test_e2e.py
@@ -111,6 +111,7 @@ async def test_404_jinja(self):
         response = requests.get("http://localhost:5050/some-random-route")
         self.assertEqual(response.status_code, 404)
         self.assertTrue("404" in response.text)
+        self.assertEqual(response.headers["Content-Type"], "text/html")
 
     async def asyncTearDown(self):
         self.proc.terminate()