diff --git a/ratelimit/core.py b/ratelimit/core.py
index 7dce35e..9c2c941 100644
--- a/ratelimit/core.py
+++ b/ratelimit/core.py
@@ -24,7 +24,7 @@ async def default_429(scope: Scope, receive: Receive, send: Send) -> None:
     return default_429
 
 
-def _on_backend_error(err) -> ASGIApp:
+def _on_backend_error(err: Exception) -> ASGIApp:
     async def default_503(scope: Scope, receive: Receive, send: Send) -> None:
         await send(
             {
@@ -51,7 +51,7 @@ def __init__(
         *,
         on_auth_error: Optional[Callable[[Exception], Awaitable[ASGIApp]]] = None,
         on_blocked: Callable[[int], ASGIApp] = _on_blocked,
-        on_backend_error: Callable[[int], ASGIApp] = _on_backend_error,
+        on_backend_error: Callable[[Exception], ASGIApp] = _on_backend_error,
     ) -> None:
         self.app = app
         self.authenticate = authenticate
diff --git a/ratelimit/exceptions/backend_connection.py b/ratelimit/exceptions.py
similarity index 52%
rename from ratelimit/exceptions/backend_connection.py
rename to ratelimit/exceptions.py
index cec419e..e868c83 100644
--- a/ratelimit/exceptions/backend_connection.py
+++ b/ratelimit/exceptions.py
@@ -1,4 +1,9 @@
-from .base_backend import BaseBackendException
+class BaseBackendException(Exception):
+    """
+    Base class for exception raised by Backends
+    """
+
+    pass
 
 
 class BackendConnectionException(BaseBackendException):
diff --git a/ratelimit/exceptions/__init__.py b/ratelimit/exceptions/__init__.py
deleted file mode 100644
index 7358eaa..0000000
--- a/ratelimit/exceptions/__init__.py
+++ /dev/null
@@ -1,3 +0,0 @@
-# flake8: noqa: F401
-from .backend_connection import BackendConnectionException
-from .base_backend import BaseBackendException
diff --git a/ratelimit/exceptions/base_backend.py b/ratelimit/exceptions/base_backend.py
deleted file mode 100644
index 4bc8abb..0000000
--- a/ratelimit/exceptions/base_backend.py
+++ /dev/null
@@ -1,6 +0,0 @@
-class BaseBackendException(Exception):
-    """
-    Base class for exception raised by Backends
-    """
-
-    pass
diff --git a/tests/test_core.py b/tests/test_core.py
index a458462..c5f3e5a 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -179,7 +179,7 @@ async def test_custom_on_backend_error():
         assert response.text == "custom 503 page"
 
 
-def yourself_503(retry_after: int):
+def yourself_503(err: Exception):
     async def inside_yourself_503(scope: Scope, receive: Receive, send: Send) -> None:
         await send({"type": "http.response.start", "status": 503})
         await send(