diff --git a/scrapy/core/downloader/middleware.py b/scrapy/core/downloader/middleware.py
index 441fc9fa6..a5619d8a4 100644
--- a/scrapy/core/downloader/middleware.py
+++ b/scrapy/core/downloader/middleware.py
@@ -40,8 +40,7 @@ class DownloaderMiddlewareManager(MiddlewareManager):
                 response = yield deferred_from_coro(method(request=request, spider=spider))
                 if response is not None and not isinstance(response, (Response, Request)):
                     raise _InvalidOutput(
-                        f"Middleware {method.__self__.__class__.__name__}"
-                        ".process_request must return None, Response or "
+                        f"Middleware {method.__qualname__} must return None, Response or "
                         f"Request, got {response.__class__.__name__}"
                     )
                 if response:
@@ -59,8 +58,7 @@ class DownloaderMiddlewareManager(MiddlewareManager):
                 response = yield deferred_from_coro(method(request=request, response=response, spider=spider))
                 if not isinstance(response, (Response, Request)):
                     raise _InvalidOutput(
-                        f"Middleware {method.__self__.__class__.__name__}"
-                        ".process_response must return Response or Request, "
+                        f"Middleware {method.__qualname__} must return Response or Request, "
                         f"got {type(response)}"
                     )
                 if isinstance(response, Request):
@@ -74,8 +72,7 @@ class DownloaderMiddlewareManager(MiddlewareManager):
                 response = yield deferred_from_coro(method(request=request, exception=exception, spider=spider))
                 if response is not None and not isinstance(response, (Response, Request)):
                     raise _InvalidOutput(
-                        f"Middleware {method.__self__.__class__.__name__}"
-                        ".process_exception must return None, Response or "
+                        f"Middleware {method.__qualname__} must return None, Response or "
                         f"Request, got {type(response)}"
                     )
                 if response:
diff --git a/scrapy/core/spidermw.py b/scrapy/core/spidermw.py
index 9a5305376..dc0e58095 100644
--- a/scrapy/core/spidermw.py
+++ b/scrapy/core/spidermw.py
@@ -22,10 +22,6 @@ def _isiterable(o):
     return isinstance(o, Iterable)
 
 
-def _fname(f):
-    return f"{f.__self__.__class__.__name__}.{f.__func__.__name__}"
-
-
 ScrapeFunc = Callable[[Union[Response, Failure], Request, Spider], Any]
 
 
@@ -53,7 +49,7 @@ class SpiderMiddlewareManager(MiddlewareManager):
             try:
                 result = method(response=response, spider=spider)
                 if result is not None:
-                    msg = (f"Middleware {_fname(method)} must return None "
+                    msg = (f"Middleware {method.__qualname__} must return None "
                            f"or raise an exception, got {type(result)}")
                     raise _InvalidOutput(msg)
             except _InvalidOutput:
@@ -91,7 +87,7 @@ class SpiderMiddlewareManager(MiddlewareManager):
             elif result is None:
                 continue
             else:
-                msg = (f"Middleware {_fname(method)} must return None "
+                msg = (f"Middleware {method.__qualname__} must return None "
                        f"or an iterable, got {type(result)}")
                 raise _InvalidOutput(msg)
         return _failure
@@ -117,7 +113,7 @@ class SpiderMiddlewareManager(MiddlewareManager):
             if _isiterable(result):
                 result = self._evaluate_iterable(response, spider, result, method_index + 1, recovered)
             else:
-                msg = (f"Middleware {_fname(method)} must return an "
+                msg = (f"Middleware {method.__qualname__} must return an "
                        f"iterable, got {type(result)}")
                 raise _InvalidOutput(msg)