diff --git a/aiogram/dispatcher/event/handler.py b/aiogram/dispatcher/event/handler.py
index bac21309..08052fd3 100644
--- a/aiogram/dispatcher/event/handler.py
+++ b/aiogram/dispatcher/event/handler.py
@@ -3,15 +3,17 @@ from dataclasses import dataclass, field
 from functools import partial
 from typing import Any, Awaitable, Callable, Dict, List, Tuple, Union
 
+from aiogram.dispatcher.filters.base import BaseFilter
+
 CallbackType = Callable[[Any], Awaitable[Any]]
 SyncFilter = Callable[[Any], Any]
 AsyncFilter = Callable[[Any], Awaitable[Any]]
-FilterType = Union[SyncFilter, AsyncFilter]
+FilterType = Union[SyncFilter, AsyncFilter, BaseFilter]
 
 
 @dataclass
 class CallableMixin:
-    callback: Callable[[Any], Any]
+    callback: Callable
     awaitable: bool = field(init=False)
     spec: inspect.FullArgSpec = field(init=False)
 
diff --git a/aiogram/dispatcher/event/observer.py b/aiogram/dispatcher/event/observer.py
index aee259e5..7f221fb4 100644
--- a/aiogram/dispatcher/event/observer.py
+++ b/aiogram/dispatcher/event/observer.py
@@ -7,7 +7,7 @@ from pydantic import ValidationError
 from ..filters.base import BaseFilter
 from .handler import CallbackType, FilterObject, FilterType, HandlerObject
 
-if TYPE_CHECKING:
+if TYPE_CHECKING:  # pragma: no cover
     from aiogram.dispatcher.router import Router
 
 
@@ -87,7 +87,7 @@ class TelegramEventObserver(EventObserver):
                 yield filter_
                 registry.append(filter_)
 
-    def register(self, callback: CallbackType, *filters: FilterType, **bound_filters):
+    def register(self, callback: CallbackType, *filters: FilterType, **bound_filters: Any):
         resolved_filters = self.resolve_filters(bound_filters)
         return super().register(callback, *filters, *resolved_filters)
 
diff --git a/aiogram/dispatcher/filters/base.py b/aiogram/dispatcher/filters/base.py
index 4d12cb69..e49db340 100644
--- a/aiogram/dispatcher/filters/base.py
+++ b/aiogram/dispatcher/filters/base.py
@@ -1,13 +1,23 @@
 from abc import ABC, abstractmethod
-from typing import Any, Dict, Union
+from typing import TYPE_CHECKING, Any, Awaitable, Callable, Dict, Union
 
 from pydantic import BaseModel
 
 
 class BaseFilter(ABC, BaseModel):
-    @abstractmethod
-    async def __call__(self, *args, **kwargs) -> Union[bool, Dict[str, Any]]:
-        pass
+    if TYPE_CHECKING:  # pragma: no cover
+        # This checking type-hint is needed because mypy checks validity of overrides and raises:
+        # error: Signature of "__call__" incompatible with supertype "BaseFilter"  [override]
+        # https://mypy.readthedocs.io/en/latest/error_code_list.html#check-validity-of-overrides-override
+
+        __call__: Any
+    else:  # pragma: no cover
+
+        @abstractmethod
+        async def __call__(
+            self, *args: Any, **kwargs: Any
+        ) -> Callable[[Any], Awaitable[Union[bool, Dict[str, Any]]]]:
+            pass
 
     def __await__(self):
         return self.__call__