diff --git a/aioesphomeapi/_frame_helper/base.pxd b/aioesphomeapi/_frame_helper/base.pxd
index e7465095..dce21f14 100644
--- a/aioesphomeapi/_frame_helper/base.pxd
+++ b/aioesphomeapi/_frame_helper/base.pxd
@@ -26,11 +26,11 @@ cdef class APIFrameHelper:
     cdef bytes _read(self, int length)
 
     @cython.locals(bytes_data=bytes)
-    cdef _add_to_buffer(self, object data)
+    cdef void _add_to_buffer(self, object data)
 
     @cython.locals(end_of_frame_pos="unsigned int")
-    cdef _remove_from_buffer(self)
+    cdef void _remove_from_buffer(self)
 
     cpdef write_packets(self, list packets, bint debug_enabled)
 
-    cdef _write_bytes(self, bytes data, bint debug_enabled)
+    cdef void _write_bytes(self, bytes data, bint debug_enabled)
diff --git a/aioesphomeapi/_frame_helper/noise.pxd b/aioesphomeapi/_frame_helper/noise.pxd
index 776da527..1604de71 100644
--- a/aioesphomeapi/_frame_helper/noise.pxd
+++ b/aioesphomeapi/_frame_helper/noise.pxd
@@ -36,22 +36,22 @@ cdef class APINoiseFrameHelper(APIFrameHelper):
         type_high="unsigned char",
         type_low="unsigned char"
     )
-    cdef _handle_frame(self, bytes frame)
+    cdef void _handle_frame(self, bytes frame)
 
     @cython.locals(
         chosen_proto=char,
         server_name_i=int
     )
-    cdef _handle_hello(self, bytes server_hello)
+    cdef void _handle_hello(self, bytes server_hello)
 
-    cdef _handle_handshake(self, bytes msg)
+    cdef void _handle_handshake(self, bytes msg)
 
-    cdef _handle_closed(self, bytes frame)
+    cdef void _handle_closed(self, bytes frame)
 
     @cython.locals(handshake_frame=bytearray, frame_len="unsigned int")
-    cdef _send_hello_handshake(self)
+    cdef void _send_hello_handshake(self)
 
-    cdef _setup_proto(self)
+    cdef void _setup_proto(self)
 
     @cython.locals(psk_bytes=bytes)
     cdef _decode_noise_psk(self)
diff --git a/aioesphomeapi/_frame_helper/noise.py b/aioesphomeapi/_frame_helper/noise.py
index 5b5ad263..efe59d58 100644
--- a/aioesphomeapi/_frame_helper/noise.py
+++ b/aioesphomeapi/_frame_helper/noise.py
@@ -135,7 +135,7 @@ def connection_made(self, transport: asyncio.BaseTransport) -> None:
 
     def data_received(self, data: bytes | bytearray | memoryview) -> None:
         self._add_to_buffer(data)
-        while self._buffer:
+        while self._buffer_len:
             self._pos = 0
             if (header := self._read(3)) is None:
                 return
diff --git a/aioesphomeapi/_frame_helper/plain_text.pxd b/aioesphomeapi/_frame_helper/plain_text.pxd
index 9a970970..f1c1e6ae 100644
--- a/aioesphomeapi/_frame_helper/plain_text.pxd
+++ b/aioesphomeapi/_frame_helper/plain_text.pxd
@@ -27,7 +27,7 @@ cdef class APIPlaintextFrameHelper(APIFrameHelper):
     )
     cpdef data_received(self, object data)
 
-    cdef _error_on_incorrect_preamble(self, object preamble)
+    cdef void _error_on_incorrect_preamble(self, object preamble)
 
     @cython.locals(
         type_="unsigned int",
diff --git a/aioesphomeapi/_frame_helper/plain_text.py b/aioesphomeapi/_frame_helper/plain_text.py
index b0d9995e..3d873c21 100644
--- a/aioesphomeapi/_frame_helper/plain_text.py
+++ b/aioesphomeapi/_frame_helper/plain_text.py
@@ -80,7 +80,7 @@ def data_received(  # pylint: disable=too-many-branches,too-many-return-statemen
         self, data: bytes | bytearray | memoryview
     ) -> None:
         self._add_to_buffer(data)
-        while self._buffer:
+        while self._buffer_len:
             # Read preamble, which should always 0x00
             # Also try to get the length and msg type
             # to avoid multiple calls to _read
diff --git a/aioesphomeapi/connection.pxd b/aioesphomeapi/connection.pxd
index c1a1005b..5b29c56d 100644
--- a/aioesphomeapi/connection.pxd
+++ b/aioesphomeapi/connection.pxd
@@ -89,7 +89,7 @@ cdef class APIConnection:
     cdef send_messages(self, tuple messages)
 
     @cython.locals(handlers=set, handlers_copy=set)
-    cpdef process_packet(self, object msg_type_proto, object data)
+    cpdef void process_packet(self, object msg_type_proto, object data)
 
     cpdef _async_cancel_pong_timer(self)