diff --git a/src/dbus_fast/_private/unmarshaller.py b/src/dbus_fast/_private/unmarshaller.py
index 8933041..c99b7cd 100644
--- a/src/dbus_fast/_private/unmarshaller.py
+++ b/src/dbus_fast/_private/unmarshaller.py
@@ -3,7 +3,7 @@ import io
 import socket
 import sys
 from struct import Struct
-from typing import Any, Callable, Dict, List, Optional, Tuple
+from typing import Any, Callable, Dict, Iterable, List, Optional, Tuple
 
 from ..constants import MESSAGE_FLAG_MAP, MESSAGE_TYPE_MAP
 from ..errors import InvalidMessageError
@@ -89,7 +89,7 @@ def build_simple_parsers(
     endian: int, can_cast: bool
 ) -> Dict[str, Callable[["Unmarshaller", SignatureType], Any]]:
     """Build a dict of parsers for simple types."""
-    parsers: Dict[str, Callable[["Unmarshaller", SignatureType], Any]] = {}
+    parsers: Dict[str, READER_TYPE] = {}
     for dbus_type, ctype_size in DBUS_TO_CTYPE.items():
         ctype, size = ctype_size
         size = ctype_size[1]
@@ -150,13 +150,13 @@ class Unmarshaller:
         "_uint32_unpack",
     )
 
-    def __init__(self, stream: io.BufferedRWPair, sock=None):
+    def __init__(self, stream: io.BufferedRWPair, sock: Optional[socket.socket] = None):
         self._unix_fds: List[int] = []
         self._buf = bytearray()  # Actual buffer
-        self._view = None  # Memory view of the buffer
+        self._view: Optional[memoryview] = None  # Memory view of the buffer
         self._stream = stream
         self._sock = sock
-        self._message: Message | None = None
+        self._message: Optional[Message] = None
         self._readers: Dict[str, READER_TYPE] = {}
         self._pos = 0
         self._body_len = 0
@@ -173,7 +173,7 @@ class Unmarshaller:
 
         Call this before processing a new message.
         """
-        self._unix_fds: List[int] = []
+        self._unix_fds = []
         self._view = None
         self._buf.clear()
         self._message = None
@@ -213,7 +213,7 @@ class Unmarshaller:
 
         return msg
 
-    def read_to_pos(self, pos) -> None:
+    def read_to_pos(self, pos: int) -> None:
         """
         Read from underlying socket into buffer.
 
@@ -310,13 +310,13 @@ class Unmarshaller:
             readers[child_type.token](self, child_type) for child_type in type_.children
         ]
 
-    def read_dict_entry(self, type_: SignatureType) -> Dict[Any, Any]:
+    def read_dict_entry(self, type_: SignatureType) -> Tuple[Any, Any]:
         self._pos += -self._pos & 7  # align 8
         return self._readers[type_.children[0].token](
             self, type_.children[0]
         ), self._readers[type_.children[1].token](self, type_.children[1])
 
-    def read_array(self, type_: SignatureType) -> List[Any]:
+    def read_array(self, type_: SignatureType) -> Iterable[Any]:
         self._pos += -self._pos & 3  # align 4 for the array
         self._pos += (
             -self._pos & (UINT32_SIZE - 1)
@@ -378,7 +378,7 @@ class Unmarshaller:
             result_list.append(reader(self, child_type))
         return result_list
 
-    def header_fields(self, header_length) -> Dict[str, Any]:
+    def header_fields(self, header_length: int) -> Dict[str, Any]:
         """Header fields are always a(yv)."""
         beginning_pos = self._pos
         headers = {}
@@ -447,7 +447,7 @@ class Unmarshaller:
         if not can_cast:
             self._uint32_unpack = UINT32_UNPACK_BY_ENDIAN[endian]
 
-    def _read_body(self):
+    def _read_body(self) -> None:
         """Read the body of the message."""
         self.read_to_pos(HEADER_SIGNATURE_SIZE + self._msg_len)
         self._view = memoryview(self._buf)
@@ -513,19 +513,17 @@ class Unmarshaller:
         INT16_DBUS_TYPE: read_int16_cast,
     }
 
-    _ctype_by_endian: Dict[
-        Tuple[int, bool], Dict[str, Tuple[None, str, int, Callable]]
-    ] = {
+    _ctype_by_endian: Dict[Tuple[int, bool], Dict[str, READER_TYPE]] = {
         endian_can_cast: build_simple_parsers(*endian_can_cast)
-        for endian_can_cast in [
+        for endian_can_cast in (
             (LITTLE_ENDIAN, True),
             (LITTLE_ENDIAN, False),
             (BIG_ENDIAN, True),
             (BIG_ENDIAN, False),
-        ]
+        )
     }
 
-    _readers_by_type: Dict[Tuple[int, bool], READER_TYPE] = {
+    _readers_by_type: Dict[Tuple[int, bool], Dict[str, READER_TYPE]] = {
         (LITTLE_ENDIAN, True): {
             **_ctype_by_endian[(LITTLE_ENDIAN, True)],
             **_complex_parsers_cast,
diff --git a/src/dbus_fast/aio/message_bus.py b/src/dbus_fast/aio/message_bus.py
index 8865e79..54f1c2c 100644
--- a/src/dbus_fast/aio/message_bus.py
+++ b/src/dbus_fast/aio/message_bus.py
@@ -423,9 +423,10 @@ class MessageBus(BaseMessageBus):
         unmarshaller = self._unmarshaller
         try:
             while True:
-                if unmarshaller.unmarshall():
+                message = unmarshaller.unmarshall()
+                if message:
                     try:
-                        self._process_message(unmarshaller.message)
+                        self._process_message(message)
                     except Exception as e:
                         logging.error(
                             f"got unexpected error processing a message: {e}.\n{traceback.format_exc()}"
diff --git a/src/dbus_fast/glib/message_bus.py b/src/dbus_fast/glib/message_bus.py
index ed7b680..c77519c 100644
--- a/src/dbus_fast/glib/message_bus.py
+++ b/src/dbus_fast/glib/message_bus.py
@@ -49,8 +49,9 @@ class _MessageSource(_GLibSource):
                 if not self.unmarshaller:
                     self.unmarshaller = Unmarshaller(self.bus._stream)
 
-                if self.unmarshaller.unmarshall():
-                    callback(self.unmarshaller.message)
+                message = self.unmarshaller.unmarshall()
+                if message:
+                    callback(message)
                     self.unmarshaller = None
                 else:
                     break