diff --git a/mcproto/packets/packet_map.py b/mcproto/packets/packet_map.py
index 9dde1310..713ea1b0 100644
--- a/mcproto/packets/packet_map.py
+++ b/mcproto/packets/packet_map.py
@@ -4,11 +4,10 @@
 import pkgutil
 from collections.abc import Iterator, Mapping, Sequence
 from functools import lru_cache
-from types import ModuleType
+from types import MappingProxyType, ModuleType
 from typing import Literal, NamedTuple, NoReturn, overload
 
 from mcproto.packets.packet import ClientBoundPacket, GameState, Packet, PacketDirection, ServerBoundPacket
-from mcproto.utils.decorators import copied_return
 
 __all__ = ["generate_packet_map"]
 
@@ -95,9 +94,8 @@ def generate_packet_map(
     ...
 
 
-@copied_return
 @lru_cache()
-def generate_packet_map(direction: PacketDirection, state: GameState) -> dict[int, type[Packet]]:
+def generate_packet_map(direction: PacketDirection, state: GameState) -> Mapping[int, type[Packet]]:
     """Dynamically generated a packet map for given ``direction`` and ``state``.
 
     This generation is done by dynamically importing all of the modules containing these packets,
@@ -124,4 +122,4 @@ def generate_packet_map(direction: PacketDirection, state: GameState) -> dict[in
             if issubclass(packet_class, direction_class):
                 packet_map[packet_class.PACKET_ID] = packet_class
 
-    return packet_map
+    return MappingProxyType(packet_map)
diff --git a/mcproto/utils/decorators.py b/mcproto/utils/decorators.py
deleted file mode 100644
index e7c04909..00000000
--- a/mcproto/utils/decorators.py
+++ /dev/null
@@ -1,29 +0,0 @@
-from __future__ import annotations
-
-from collections.abc import Callable
-from functools import wraps
-from typing import Protocol, TypeVar
-
-from typing_extensions import ParamSpec
-
-__all__ = ["copied_return"]
-
-T = TypeVar("T")
-
-
-class SupportsCopy(Protocol):
-    def copy(self: T) -> T:
-        ...
-
-
-P = ParamSpec("P")
-R_Copyable = TypeVar("R_Copyable", bound=SupportsCopy)
-
-
-def copied_return(func: Callable[P, R_Copyable]) -> Callable[P, R_Copyable]:
-    @wraps(func)
-    def wrapper(*args: P.args, **kwargs: P.kwargs) -> R_Copyable:
-        ret = func(*args, **kwargs)
-        return ret.copy()
-
-    return wrapper