diff --git a/README.md b/README.md
index ce3a470..cc0851a 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # Robust And Fast Functional IO Toolkit
 
-*Raffiot* is small (almost) dependency-free python library providing some
+*Raffiot* is small dependency-free python library providing some
 usual functional tools. It currently provides
 - an easy-to-use `IO` monad which is **stack-safe**, **fast**, support
   **asynchronous**, **concurrent**, **parallel** programming, has many other features.
@@ -35,10 +35,9 @@ The [API](https://chrilves.github.io/raffiot.py/api/index.html) is online at
 
 ## Features
 
-- **pure python**: *Raffiot* is written entirely in Python 3.7+.
+- **pure python**: *Raffiot* is written entirely in Python 3.8+.
 - **small**: it is just a few small files.
-- **(almost) dependency-free**: it only depends on `typing-extensions` (for the
-  `@final` annotation).
+- **dependency-free**: it only depends on the python standary library.
 - **crystal clear code** 
 
 ### IO
@@ -72,4 +71,4 @@ result of a computation:
 - `Ok(value)`: the computation successfully computed the this `value`.
 - `Error(error)`: the computation failed on some expected failure `error`, probably
    from the business domain.
-- `Panic(exception)`: the computation failed on some unexpected failure `exception`.
\ No newline at end of file
+- `Panic(exception)`: the computation failed on some unexpected failure `exception`.
diff --git a/raffiot/_internal.py b/raffiot/_internal.py
index ce2fa9d..16a926f 100644
--- a/raffiot/_internal.py
+++ b/raffiot/_internal.py
@@ -8,8 +8,7 @@
 
 from enum import Enum
 
-from typing_extensions import final
-from typing import List, Any, Iterable
+from typing import List, Any, Iterable, final
 from collections import abc
 
 __all__ = ["IOTag", "ContTag", "ResultTag", "FiberState"]
diff --git a/raffiot/_runtime.py b/raffiot/_runtime.py
index feadb83..ec7caf2 100644
--- a/raffiot/_runtime.py
+++ b/raffiot/_runtime.py
@@ -16,9 +16,7 @@
 from queue import Queue
 from random import randint
 from threading import Thread
-from typing import Any, List, TypeVar, Generic, Callable, Optional, Tuple
-
-from typing_extensions import final
+from typing import Any, List, TypeVar, Generic, Callable, Optional, Tuple, final
 
 from raffiot._internal import ContTag, FiberState, IOTag, ResultTag
 from raffiot.io import IO
diff --git a/raffiot/io.py b/raffiot/io.py
index e87ad24..5f6cbaa 100644
--- a/raffiot/io.py
+++ b/raffiot/io.py
@@ -6,9 +6,7 @@
 
 import time
 from collections import abc
-from typing import TypeVar, Generic, Callable, Any, List, Iterable
-
-from typing_extensions import final
+from typing import TypeVar, Generic, Callable, Any, List, Iterable, final
 
 from raffiot import result
 from raffiot._internal import IOTag
diff --git a/raffiot/resource.py b/raffiot/resource.py
index 5801144..0bd6d92 100644
--- a/raffiot/resource.py
+++ b/raffiot/resource.py
@@ -7,9 +7,7 @@
 
 from collections import abc
 from dataclasses import dataclass
-from typing import TypeVar, Generic, Callable, Any, Tuple, List, Iterable
-
-from typing_extensions import final
+from typing import TypeVar, Generic, Callable, Any, Tuple, List, Iterable, final
 
 from raffiot import _runtime
 from raffiot import io
diff --git a/raffiot/result.py b/raffiot/result.py
index 5db1271..12ebb12 100644
--- a/raffiot/result.py
+++ b/raffiot/result.py
@@ -6,9 +6,7 @@
 
 from collections import abc
 from dataclasses import dataclass
-from typing import TypeVar, Generic, Callable, Any, List, Iterable, Union
-
-from typing_extensions import final
+from typing import TypeVar, Generic, Callable, Any, List, Iterable, Union, final
 
 from raffiot.utils import (
     ComputationStatus,
diff --git a/raffiot/utils.py b/raffiot/utils.py
index 1b6a1e6..72594af 100644
--- a/raffiot/utils.py
+++ b/raffiot/utils.py
@@ -4,9 +4,7 @@
 from dataclasses import dataclass
 from enum import IntEnum
 from traceback import format_exc, format_stack
-from typing import Any, List, Generic, TypeVar, Iterable
-
-from typing_extensions import final
+from typing import Any, List, Generic, TypeVar, Iterable, final
 
 __all__ = [
     "TracedException",
diff --git a/raffiot/val.py b/raffiot/val.py
index c14eb0b..71d7c36 100644
--- a/raffiot/val.py
+++ b/raffiot/val.py
@@ -7,9 +7,7 @@
 
 from collections import abc
 from dataclasses import dataclass
-from typing import Generic, TypeVar, Callable, List, Any
-
-from typing_extensions import final
+from typing import Generic, TypeVar, Callable, List, Any, final
 
 from raffiot import io, resource
 from raffiot.io import IO
diff --git a/raffiot/var.py b/raffiot/var.py
index d2ca7db..04ae79c 100644
--- a/raffiot/var.py
+++ b/raffiot/var.py
@@ -8,9 +8,7 @@
 
 from collections import abc
 from dataclasses import dataclass
-from typing import Generic, TypeVar, Callable, List, Any, Tuple
-
-from typing_extensions import final
+from typing import Generic, TypeVar, Callable, List, Any, Tuple, final
 
 from raffiot import io, resource
 from raffiot.io import IO
diff --git a/setup.py b/setup.py
index fe67ef3..bda2f22 100755
--- a/setup.py
+++ b/setup.py
@@ -31,13 +31,13 @@
         "Intended Audience :: Developers",
         "Topic :: Software Development :: Build Tools",
         "License :: OSI Approved :: Apache Software License",
-        "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
+        "Programming Language :: Python :: 3.10",
         "Operating System :: OS Independent",
     ],
-    install_requires=["typing-extensions"],
-    python_requires=">=3.7",
+    install_requires=[],
+    python_requires=">=3.8",
     zip_safe=False,
     package_data={"raffiot": ["py.typed"]},
 )