diff --git a/stdlib/_typeshed/__init__.pyi b/stdlib/_typeshed/__init__.pyi
index b0ee1f4ad48a..849078e9462e 100644
--- a/stdlib/_typeshed/__init__.pyi
+++ b/stdlib/_typeshed/__init__.pyi
@@ -234,6 +234,7 @@ else:
     WriteableBuffer: TypeAlias = bytearray | memoryview | array.array[Any] | mmap.mmap | ctypes._CData  # stable
 # Same as _WriteableBuffer, but also includes read-only buffer types (like bytes).
 ReadableBuffer: TypeAlias = ReadOnlyBuffer | WriteableBuffer  # stable
+_BufferWithLen: TypeAlias = ReadableBuffer  # not stable  # noqa: Y047
 
 ExcInfo: TypeAlias = tuple[type[BaseException], BaseException, TracebackType]
 OptExcInfo: TypeAlias = Union[ExcInfo, tuple[None, None, None]]
diff --git a/stdlib/binhex.pyi b/stdlib/binhex.pyi
index 639d30d1d0de..e0993c840ce7 100644
--- a/stdlib/binhex.pyi
+++ b/stdlib/binhex.pyi
@@ -1,3 +1,4 @@
+from _typeshed import _BufferWithLen
 from typing import IO, Any
 from typing_extensions import Literal, TypeAlias
 
@@ -27,9 +28,9 @@ class openrsrc:
 
 class BinHex:
     def __init__(self, name_finfo_dlen_rlen: _FileInfoTuple, ofp: _FileHandleUnion) -> None: ...
-    def write(self, data: bytes) -> None: ...
+    def write(self, data: _BufferWithLen) -> None: ...
     def close_data(self) -> None: ...
-    def write_rsrc(self, data: bytes) -> None: ...
+    def write_rsrc(self, data: _BufferWithLen) -> None: ...
     def close(self) -> None: ...
 
 def binhex(inp: str, out: str) -> None: ...