diff --git a/build.py b/build.py
index c9f9131..cc8bc17 100644
--- a/build.py
+++ b/build.py
@@ -22,6 +22,7 @@ def build(setup_kwargs):
             dict(
                 ext_modules=cythonize(
                     [
+                        "src/dbus_fast/aio/message_reader.py",
                         "src/dbus_fast/message.py",
                         "src/dbus_fast/signature.py",
                         "src/dbus_fast/unpack.py",
diff --git a/src/dbus_fast/aio/message_bus.py b/src/dbus_fast/aio/message_bus.py
index 54f1c2c..b0941f6 100644
--- a/src/dbus_fast/aio/message_bus.py
+++ b/src/dbus_fast/aio/message_bus.py
@@ -24,6 +24,7 @@ from ..errors import AuthError
 from ..message import Message
 from ..message_bus import BaseMessageBus
 from ..service import ServiceInterface
+from .message_reader import build_message_reader
 from .proxy_object import ProxyObject
 
 
@@ -193,7 +194,14 @@ class MessageBus(BaseMessageBus):
 
         future = self._loop.create_future()
 
-        self._loop.add_reader(self._fd, self._message_reader)
+        self._loop.add_reader(
+            self._fd,
+            build_message_reader(
+                self._unmarshaller,
+                self._process_message,
+                self._finalize,
+            ),
+        )
 
         def on_hello(reply, err):
             try:
@@ -419,24 +427,6 @@ class MessageBus(BaseMessageBus):
 
         return handler
 
-    def _message_reader(self) -> None:
-        unmarshaller = self._unmarshaller
-        try:
-            while True:
-                message = unmarshaller.unmarshall()
-                if message:
-                    try:
-                        self._process_message(message)
-                    except Exception as e:
-                        logging.error(
-                            f"got unexpected error processing a message: {e}.\n{traceback.format_exc()}"
-                        )
-                    unmarshaller.reset()
-                else:
-                    break
-        except Exception as e:
-            self._finalize(e)
-
     async def _auth_readline(self) -> str:
         buf = b""
         while buf[-2:] != b"\r\n":
diff --git a/src/dbus_fast/aio/message_reader.pxd b/src/dbus_fast/aio/message_reader.pxd
new file mode 100644
index 0000000..a53a8e3
--- /dev/null
+++ b/src/dbus_fast/aio/message_reader.pxd
@@ -0,0 +1,3 @@
+"""cdefs for message_reader.py"""
+
+import cython
diff --git a/src/dbus_fast/aio/message_reader.py b/src/dbus_fast/aio/message_reader.py
new file mode 100644
index 0000000..4da1f08
--- /dev/null
+++ b/src/dbus_fast/aio/message_reader.py
@@ -0,0 +1,35 @@
+import logging
+import traceback
+from typing import Callable, Optional
+
+from .._private.unmarshaller import Unmarshaller
+from ..message import Message
+
+
+def build_message_reader(
+    unmarshaller: Unmarshaller,
+    process: Callable[[Message], None],
+    finalize: Callable[[Optional[Exception]], None],
+) -> None:
+    """Build a callable that reads messages from the unmarshaller and passes them to the process function."""
+    unmarshall = unmarshaller.unmarshall
+    reset = unmarshaller.reset
+
+    def _message_reader() -> None:
+        """Reads messages from the unmarshaller and passes them to the process function."""
+        try:
+            while True:
+                message = unmarshall()
+                if not message:
+                    return
+                try:
+                    process(message)
+                except Exception as e:
+                    logging.error(
+                        f"got unexpected error processing a message: {e}.\n{traceback.format_exc()}"
+                    )
+                reset()
+        except Exception as e:
+            finalize(e)
+
+    return _message_reader