--- a/src/dbus_fast/_private/marshaller.py
+++ b/src/dbus_fast/_private/marshaller.py
@@ -107,7 +107,7 @@
     ) -> int:
         written = self._align(4)
         # length placeholder
-        buf: bytearray = self._buf
+        buf = self._buf
         offset = len(buf)
         written += self._align(4) + 4
         buf += PACKED_UINT32_ZERO
--- a/src/dbus_fast/_private/unmarshaller.py
+++ b/src/dbus_fast/_private/unmarshaller.py
@@ -628,7 +628,7 @@
         if cython.compiled:
             if self._buf_len <= self._pos:
                 raise IndexError("Not enough data to read signature")
-        result: Variant | None = None
+        result = None
         signature_len = self._buf_ustr[self._pos]
         if signature_len == 1:
             self._pos += 3  # 1 len byte + 1 signature char + 1 null terminator
@@ -945,7 +945,7 @@
         header_signature = header_fields[HEADER_SIGNATURE_IDX]
         if not self._body_len:
             tree = SIGNATURE_TREE_EMPTY
-            body: list[Any] = []
+            body = []
         elif type(header_signature) is not str or not header_signature:
             # A non-empty body requires a valid signature header field
             # (spec §4.1). A forged frame may omit it (None), send it empty, or
@@ -955,7 +955,7 @@
                 "message has a body but no valid signature header field"
             )
         else:
-            signature: str = header_signature
+            signature = header_signature
             token_as_int = ord(signature[0])
             if len(signature) == 1:
                 if token_as_int == TOKEN_O_AS_INT:
--- a/src/dbus_fast/message_bus.py
+++ b/src/dbus_fast/message_bus.py
@@ -956,7 +956,7 @@
         return None
 
     def _find_any_message_handler_matching_signature(
-        self, interfaces: dict[str, ServiceInterface], msg: _Message
+        self, interfaces, msg: _Message
     ) -> HandlerType | None:
         # No interface, so we need to search all interfaces for the method
         # with a matching signature
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -50,7 +50,7 @@
 pytest-asyncio = ">=0.19,<1.5"
 pycairo = "^1.21.0"
 PyGObject = {version = ">=3.50,<3.57", python = "<4"}
-Cython = ">=3,<3.3.0"
+Cython = ">=3,<3.4"
 setuptools = ">=65.4.1,<83.0.0"
 pytest-timeout = "^2.1.0"
 pytest-codspeed = ">=3.1.1,<6.0.0"
@@ -117,7 +117,7 @@
 ignore_errors = true
 
 [build-system]
-requires = ['setuptools>=65.4.1', 'wheel', 'Cython>=3,<3.3.0', "poetry-core>=1.0.0"]
+requires = ['setuptools>=65.4.1', 'wheel', 'Cython>=3,<3.4', "poetry-core>=1.0.0"]
 build-backend = "poetry.core.masonry.api"
 
 [tool.ruff]