diff --git a/aiosmtpd/docs/proxyprotocol.rst b/aiosmtpd/docs/proxyprotocol.rst
index eac41b0a..d5a3b650 100644
--- a/aiosmtpd/docs/proxyprotocol.rst
+++ b/aiosmtpd/docs/proxyprotocol.rst
@@ -203,7 +203,7 @@ Enums
       Valid only for address family of :attr:`AF.INET` or :attr:`AF.INET6`
 
    .. py:attribute:: rest
-      :type: ByteString
+      :type: bytearray
 
       The contents depend on the version of the PROXY header *and* (for version 2)
       the address family.
@@ -374,7 +374,7 @@ Enums
    .. py:classmethod:: from_raw(raw) -> Optional[ProxyTLV]
 
       :param raw: The raw bytes containing the TLV Vectors
-      :type raw: ByteString
+      :type raw: bytearray
       :return: A new instance of ProxyTLV, or ``None`` if parsing failed
 
       This triggers the parsing of raw bytes/bytearray into a ProxyTLV instance.
@@ -387,7 +387,7 @@ Enums
    .. py:classmethod:: parse(chunk, partial_ok=True) -> Dict[str, Any]
 
       :param chunk: The bytes to parse into TLV Vectors
-      :type chunk: ByteString
+      :type chunk: bytearray
       :param partial_ok: If ``True``, return partially-parsed TLV Vectors as is.
          If ``False``, (re)raise ``MalformedTLV``
       :type partial_ok: bool
diff --git a/aiosmtpd/proxy_protocol.py b/aiosmtpd/proxy_protocol.py
index b5be17cb..3395b35b 100644
--- a/aiosmtpd/proxy_protocol.py
+++ b/aiosmtpd/proxy_protocol.py
@@ -9,7 +9,7 @@
 from enum import IntEnum
 from functools import partial
 from ipaddress import IPv4Address, IPv6Address, ip_address
-from typing import Any, ByteString, Dict, Optional, Protocol, Tuple, Union
+from typing import Any, Dict, Optional, Protocol, Tuple, Union
 
 import attr
 from public import public
@@ -165,7 +165,7 @@ def same_attribs(self, _raises: bool = False, **kwargs) -> bool:
     @classmethod
     def parse(
         cls,
-        data: ByteString,
+        data: bytearray,
         partial_ok: bool = True,
         strict: bool = False,
     ) -> Tuple[Dict[str, Any], Dict[str, int]]:
@@ -179,7 +179,7 @@ def parse(
         rslt: Dict[str, Any] = {}
         tlv_loc: Dict[str, int] = {}
 
-        def _pars(chunk: ByteString, *, offset: int) -> None:
+        def _pars(chunk: bytearray, *, offset: int) -> None:
             i = 0
             while i < len(chunk):
                 typ = chunk[i]
@@ -218,7 +218,7 @@ def _pars(chunk: ByteString, *, offset: int) -> None:
 
     @classmethod
     def from_raw(
-        cls, raw: ByteString, strict: bool = False
+        cls, raw: bytearray, strict: bool = False
     ) -> Optional["ProxyTLV"]:
         """
         Parses raw bytes for TLV Vectors, decode them and giving them human-readable
@@ -265,7 +265,7 @@ class ProxyData:
     dst_addr: Optional[EndpointAddress] = _anoinit(default=None)
     src_port: Optional[int] = _anoinit(default=None)
     dst_port: Optional[int] = _anoinit(default=None)
-    rest: ByteString = _anoinit(default=b"")
+    rest: bytearray = _anoinit(default=b"")
     """
     Rest of PROXY Protocol data following UNKNOWN (v1) or UNSPEC (v2), or containing
     undecoded TLV (v2). If the latter, you can use the ProxyTLV class to parse the
@@ -340,7 +340,7 @@ def __bool__(self) -> bool:
 # Reference: https://github.com/haproxy/haproxy/blob/v2.3.0/doc/proxy-protocol.txt
 
 
-async def _get_v1(reader: AsyncReader, initial: ByteString = b"") -> ProxyData:
+async def _get_v1(reader: AsyncReader, initial: bytearray = b"") -> ProxyData:
     proxy_data = ProxyData(version=1)
     proxy_data.whole_raw = bytearray(initial)
 
@@ -424,7 +424,7 @@ async def get_ap(matcher: "re.Pattern[str]") -> str:
     return proxy_data
 
 
-async def _get_v2(reader: AsyncReader, initial: ByteString = b"") -> ProxyData:
+async def _get_v2(reader: AsyncReader, initial: bytearray = b"") -> ProxyData:
     proxy_data = ProxyData(version=2)
     whole_raw = bytearray()