diff --git a/aiogram/dispatcher/handler.py b/aiogram/dispatcher/handler.py
index cd5e9b50..da37fe3a 100644
--- a/aiogram/dispatcher/handler.py
+++ b/aiogram/dispatcher/handler.py
@@ -44,6 +44,10 @@ class Handler:
         self.handlers: List[Handler.HandlerObj] = []
         self.middleware_key = middleware_key
 
+    @property
+    def formatted_middleware_key(self):
+        return "pre_process_"+self.middleware_key
+
     def register(self, handler, filters=None, index=None):
         """
         Register callback
@@ -98,7 +102,7 @@ class Handler:
 
         if self.middleware_key:
             try:
-                await self.dispatcher.middleware.trigger(f"pre_process_{self.middleware_key}", args + (data,))
+                await self.dispatcher.middleware.trigger(self.formatted_middleware_key, args + (data,))
             except CancelHandler:  # Allow to cancel current event
                 return results
 
@@ -112,7 +116,7 @@ class Handler:
                     ctx_token = current_handler.set(handler_obj.handler)
                     try:
                         if self.middleware_key:
-                            await self.dispatcher.middleware.trigger(f"process_{self.middleware_key}", args + (data,))
+                            await self.dispatcher.middleware.trigger(self.formatted_middleware_key, args + (data,))
                         partial_data = _check_spec(handler_obj.spec, data)
                         response = await handler_obj.handler(*args, **partial_data)
                         if response is not None:
@@ -127,7 +131,7 @@ class Handler:
                         current_handler.reset(ctx_token)
         finally:
             if self.middleware_key:
-                await self.dispatcher.middleware.trigger(f"post_process_{self.middleware_key}",
+                await self.dispatcher.middleware.trigger(f"post_process_"+self.middleware_key,
                                                          args + (results, data,))
 
         return results
diff --git a/aiogram/dispatcher/middlewares.py b/aiogram/dispatcher/middlewares.py
index dba3db4c..6534a164 100644
--- a/aiogram/dispatcher/middlewares.py
+++ b/aiogram/dispatcher/middlewares.py
@@ -35,7 +35,7 @@ class MiddlewareManager:
 
         self.applications.append(middleware)
         middleware.setup(self)
-        log.debug(f"Loaded middleware '{middleware.__class__.__name__}'")
+        log.debug(f"Loaded middleware "+repr(middleware.__class__.__name__))
         return middleware
 
     async def trigger(self, action: str, args: typing.Iterable):
@@ -96,7 +96,7 @@ class BaseMiddleware:
         :param args:
         :return:
         """
-        handler_name = f"on_{action}"
+        handler_name = f"on_"+action
         handler = getattr(self, handler_name, None)
         if not handler:
             return None
diff --git a/aiogram/dispatcher/storage.py b/aiogram/dispatcher/storage.py
index a2992322..9a734251 100644
--- a/aiogram/dispatcher/storage.py
+++ b/aiogram/dispatcher/storage.py
@@ -444,7 +444,7 @@ class FSMContextProxy:
         return item in self._data
 
     def __str__(self):
-        readable_state = f"'{self.state}'" if self.state else "<default>"
+        readable_state = repr(str(self.state)) if self.state else "<default>"
         result = f"{self.__class__.__name__} state = {readable_state}, data = {self._data}"
         if self._closed:
             result += ', closed = True'
@@ -495,6 +495,6 @@ class DisabledStorage(BaseStorage):
 
     @staticmethod
     def _warn():
-        warn(f"You haven’t set any storage yet so no states and no data will be saved. \n"
-             f"You can connect MemoryStorage for debug purposes or non-essential data.",
+        warn("You haven’t set any storage yet so no states and no data will be saved. \n"
+             "You can connect MemoryStorage for debug purposes or non-essential data.",
              FSMStorageWarning, 5)
diff --git a/aiogram/dispatcher/webhook.py b/aiogram/dispatcher/webhook.py
index 135fe21e..47317afd 100644
--- a/aiogram/dispatcher/webhook.py
+++ b/aiogram/dispatcher/webhook.py
@@ -203,9 +203,9 @@ class WebhookRequestHandler(web.View):
         :param task:
         :return:
         """
-        warn(f"Detected slow response into webhook. "
+        warn("Detected slow response into webhook. "
              f"(Greater than {RESPONSE_TIMEOUT} seconds)\n"
-             f"Recommended to use 'async_task' decorator from Dispatcher for handler with long timeouts.",
+             "Recommended to use 'async_task' decorator from Dispatcher for handler with long timeouts.",
              TimeoutWarning)
 
         dispatcher = self.get_dispatcher()
@@ -261,7 +261,7 @@ class WebhookRequestHandler(web.View):
         if self.request.app.get('_check_ip', False):
             ip_address, accept = self.check_ip()
             if not accept:
-                log.warning(f"Blocking request from an unauthorized IP: {ip_address}")
+                log.warning(f"Blocking request from an unauthorized IP: "+ip_address)
                 raise web.HTTPUnauthorized()
 
             # context.set_value('TELEGRAM_IP', ip_address)