diff --git a/av/packet.pyi b/av/packet.pyi
index 91775eff7..14b4b0bce 100644
--- a/av/packet.pyi
+++ b/av/packet.pyi
@@ -1,5 +1,6 @@
+from collections.abc import Buffer
 from fractions import Fraction
-from typing import Buffer, Iterator
+from typing import Iterator
 
 from av.subtitles.subtitle import SubtitleSet
 
@@ -22,3 +23,4 @@ class Packet(Buffer):
 
     def __init__(self, input: int | bytes | None = None) -> None: ...
     def decode(self) -> Iterator[SubtitleSet]: ...
+    def __buffer__(self, arg1) -> memoryview: ...
diff --git a/tests/test_bitstream.py b/tests/test_bitstream.py
index 937448fe5..8538594a7 100644
--- a/tests/test_bitstream.py
+++ b/tests/test_bitstream.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import av
 from av import Packet
 from av.bitstream import BitStreamFilterContext, bitstream_filters_available
@@ -5,7 +7,10 @@
 from .common import TestCase, fate_suite
 
 
-def is_annexb(packet: Packet) -> bool:
+def is_annexb(packet: Packet | bytes | None) -> bool:
+    if packet is None:
+        return False
+
     data = bytes(packet)
     return data[:3] == b"\0\0\x01" or data[:4] == b"\0\0\0\x01"