diff --git a/umsgpack/__init__.pyi b/umsgpack/__init__.pyi
index 61a8413..a610978 100644
--- a/umsgpack/__init__.pyi
+++ b/umsgpack/__init__.pyi
@@ -1,30 +1,44 @@
-from typing import Any
+from typing import Any, Callable, Type, TypeVar
+
+try:
+    from typing import Protocol
+except ImportError:
+    _SupportsRead = Any
+    _SupportsWrite = Any
+else:
+    class _SupportsRead(Protocol):
+        def read(self, __size: int) -> bytes: ...
+
+    class _SupportsWrite(Protocol):
+        def write(self, __data: bytes) -> Any: ...
+
+_T = TypeVar("_T")
 
 __version__: str
 
 version: tuple[int, int, int]
 
-def pack(obj, fp, **options) -> None: ...
-def packb(obj, **options) -> bytes: ...
-def dump(obj, fp, **options) -> None: ...
-def dumps(obj, **options) -> bytes: ...
+def pack(obj: Any, fp: _SupportsWrite, **options: Any) -> None: ...
+def packb(obj: Any, **options: Any) -> bytes: ...
+def dump(obj: Any, fp: _SupportsWrite, **options: Any) -> None: ...
+def dumps(obj: Any, **options: Any) -> bytes: ...
 
-def unpackb(s: bytes | bytearray, **options) -> Any: ...
-def unpack(fp, **options) -> Any: ...
-def loads(s: bytes | bytearray, **options) -> Any: ...
-def load(fp, **options) -> Any: ...
+def unpackb(s: bytes | bytearray, **options: Any) -> Any: ...
+def unpack(fp: _SupportsRead, **options: Any) -> Any: ...
+def loads(s: bytes | bytearray, **options: Any) -> Any: ...
+def load(fp: _SupportsRead, **options: Any) -> Any: ...
 
 class Ext:
     type: int
     data: bytes
     def __init__(self, type: int, data: bytes) -> None: ...
-    def __eq__(self, other) -> bool: ...
-    def __ne__(self, other) -> bool: ...
+    def __eq__(self, other: object) -> bool: ...
+    def __ne__(self, other: object) -> bool: ...
     def __hash__(self) -> int: ...
 
 class InvalidString(bytes): ...
 
-def ext_serializable(ext_type: int): ...
+def ext_serializable(ext_type: int) -> Callable[[Type[_T]], Type[_T]]: ...
 
 class PackException(Exception): ...
 class UnpackException(Exception): ...