diff --git a/build_ext.py b/build_ext.py
index 9be33690..5eaf0a37 100644
--- a/build_ext.py
+++ b/build_ext.py
@@ -25,6 +25,7 @@ def build(setup_kwargs):
                         "src/dbus_fast/aio/message_reader.py",
                         "src/dbus_fast/message.py",
                         "src/dbus_fast/message_bus.py",
+                        "src/dbus_fast/service.py",
                         "src/dbus_fast/signature.py",
                         "src/dbus_fast/unpack.py",
                         "src/dbus_fast/_private/marshaller.py",
diff --git a/src/dbus_fast/message_bus.pxd b/src/dbus_fast/message_bus.pxd
index 01a182fb..d3ea2046 100644
--- a/src/dbus_fast/message_bus.pxd
+++ b/src/dbus_fast/message_bus.pxd
@@ -1,15 +1,17 @@
 import cython
 
 from .message cimport Message
+from .service cimport ServiceInterface, _Method
 
 
 cdef object MessageType
 cdef object DBusError
 cdef object MessageFlag
-cdef object ServiceInterface
 
 cdef object MESSAGE_TYPE_CALL
 cdef object MESSAGE_TYPE_SIGNAL
+cdef object assert_object_path_valid
+cdef object assert_bus_name_valid
 
 cdef class SendReply:
 
@@ -39,4 +41,8 @@ cdef class BaseMessageBus:
 
     cpdef _process_message(self, Message msg)
 
+    @cython.locals(
+        method=_Method,
+        interface=ServiceInterface
+    )
     cdef _find_message_handler(self, Message msg)
diff --git a/src/dbus_fast/message_bus.py b/src/dbus_fast/message_bus.py
index 9327bc22..3dc9e3ab 100644
--- a/src/dbus_fast/message_bus.py
+++ b/src/dbus_fast/message_bus.py
@@ -886,7 +886,16 @@ def handler(msg: Message, send_reply: Callable[[Message], None]) -> None:
                 signature_tree=method.out_signature_tree,
                 replace_fds=self._negotiate_unix_fd,
             )
-            send_reply(Message.new_method_return(msg, method.out_signature, body, fds))
+            send_reply(
+                Message(
+                    message_type=MessageType.METHOD_RETURN,
+                    reply_serial=msg.serial,
+                    destination=msg.sender,
+                    signature=method.out_signature,
+                    body=body,
+                    unix_fds=fds,
+                )
+            )
 
         return handler
 
diff --git a/src/dbus_fast/service.pxd b/src/dbus_fast/service.pxd
new file mode 100644
index 00000000..b15c7bd7
--- /dev/null
+++ b/src/dbus_fast/service.pxd
@@ -0,0 +1,24 @@
+"""cdefs for service.py"""
+
+import cython
+
+
+cdef class _Method:
+
+    cdef public object name
+    cdef public object fn
+    cdef public object disabled
+    cdef public object introspection
+    cdef public object in_signature
+    cdef public object out_signature
+    cdef public object in_signature_tree
+    cdef public object out_signature_tree
+
+cdef class ServiceInterface:
+
+    cdef public object name
+    cdef list __methods
+    cdef list __properties
+    cdef list __signals
+    cdef set __buses
+    cdef dict __handlers