diff --git a/.github/workflows/codeqa-test.yml b/.github/workflows/codeqa-test.yml
index c068ee3..5f0bb03 100644
--- a/.github/workflows/codeqa-test.yml
+++ b/.github/workflows/codeqa-test.yml
@@ -19,9 +19,9 @@ jobs:
         path: ~/.cache/pip
         key: pip-lint
     - name: Install dependencies
-      run: pip install flake8 isort
+      run: pip install pyproject-flake8 isort
     - name: Run flake8
-      run: flake8 sphinx_autodoc_typehints.py tests
+      run: pflake8 sphinx_autodoc_typehints.py tests
     - name: Run isort
       run: isort -c sphinx_autodoc_typehints.py tests
 
@@ -31,7 +31,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        python-version: [3.6, 3.7, 3.8, 3.9, 3.10.0-alpha.5]
+        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10"]
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v2
diff --git a/pre-commit-config.sample.yaml b/.pre-commit-config.yaml
similarity index 85%
rename from pre-commit-config.sample.yaml
rename to .pre-commit-config.yaml
index 7f86457..00f00ce 100644
--- a/pre-commit-config.sample.yaml
+++ b/.pre-commit-config.yaml
@@ -22,3 +22,7 @@ repos:
     hooks:
     - id: isort
       additional_dependencies: [toml]
+-   repo: https://github.com/csachs/pyproject-flake8
+    rev: v0.0.1a2.post1
+    hooks:
+    - id: pyproject-flake8
diff --git a/pyproject.toml b/pyproject.toml
index eeb699e..68d7eab 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -14,6 +14,9 @@ multi_line_output = 4
 [tool.autopep8]
 max_line_length = 99
 
+[tool.flake8]
+max-line-length = 99
+
 [tool.pytest.ini_options]
 addopts = "-rsx --tb=short"
 testpaths = ["tests"]
diff --git a/setup.cfg b/setup.cfg
index c872ff3..4e57ff5 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -38,10 +38,3 @@ test =
     Sphinx >= 3.2.0
 type_comments =
     typed_ast >= 1.4.0; python_version < "3.8"
-
-[flake8]
-max-line-length = 99
-
-[tool:pytest]
-addopts = -rsx --tb=short
-testpaths = tests
diff --git a/sphinx_autodoc_typehints.py b/sphinx_autodoc_typehints.py
index 0b69b1c..5a4ed95 100644
--- a/sphinx_autodoc_typehints.py
+++ b/sphinx_autodoc_typehints.py
@@ -170,13 +170,19 @@ def normalize_source_lines(sourcelines: str) -> str:
     for i, l in enumerate(sourcelines):
         if l.lstrip().startswith("def"):
             idx = i
+            whitespace_separator = "def"
             break
+        elif l.lstrip().startswith("async def"):
+            idx = i
+            whitespace_separator = "async def"
+            break
+
     else:
         return "\n".join(sourcelines)
     fn_def = sourcelines[idx]
 
     # Get a string representing the amount of leading whitespace
-    whitespace = fn_def.split("def")[0]
+    whitespace = fn_def.split(whitespace_separator)[0]
 
     # Add this leading whitespace to all lines before and after the `def`
     aligned_prefix = [whitespace + remove_prefix(s, whitespace) for s in sourcelines[:idx]]
@@ -251,15 +257,37 @@ def process_signature(app, what: str, name: str, obj, options, signature, return
     return stringify_signature(signature).replace('\\', '\\\\'), None
 
 
+def _future_annotations_imported(obj):
+    if sys.version_info < (3, 7):
+        # Only Python ≥ 3.7 supports PEP563.
+        return False
+
+    _annotations = getattr(inspect.getmodule(obj), "annotations", None)
+    if _annotations is None:
+        return False
+
+    # Make sure that annotations is imported from __future__
+    CO_FUTURE_ANNOTATIONS = 0x1000000  # defined in cpython/Lib/__future__.py
+    return _annotations.compiler_flag == CO_FUTURE_ANNOTATIONS
+
+
 def get_all_type_hints(obj, name):
     rv = {}
 
     try:
         rv = get_type_hints(obj)
-    except (AttributeError, TypeError, RecursionError):
+    except (AttributeError, TypeError, RecursionError) as exc:
         # Introspecting a slot wrapper will raise TypeError, and and some recursive type
         # definitions will cause a RecursionError (https://github.com/python/typing/issues/574).
-        pass
+
+        # If one is using PEP563 annotations, Python will raise a (e.g.,)
+        # TypeError("TypeError: unsupported operand type(s) for |: 'type' and 'NoneType'")
+        # on 'str | None', therefore we accept TypeErrors with that error message
+        # if 'annotations' is imported from '__future__'.
+        if (isinstance(exc, TypeError)
+            and _future_annotations_imported(obj)
+                and "unsupported operand type" in str(exc)):
+            rv = obj.__annotations__
     except NameError as exc:
         logger.warning('Cannot resolve forward reference in type annotations of "%s": %s',
                        name, exc)
diff --git a/tests/roots/test-dummy/dummy_module_future_annotations.py b/tests/roots/test-dummy/dummy_module_future_annotations.py
new file mode 100644
index 0000000..119159d
--- /dev/null
+++ b/tests/roots/test-dummy/dummy_module_future_annotations.py
@@ -0,0 +1,11 @@
+from __future__ import annotations
+
+
+def function_with_py310_annotations(self, x: bool, y: int, z: str | None = None) -> str:
+    """
+    Method docstring.
+
+    :param x: foo
+    :param y: bar
+    :param z: baz
+    """
diff --git a/tests/roots/test-dummy/future_annotations.rst b/tests/roots/test-dummy/future_annotations.rst
new file mode 100644
index 0000000..3d774cb
--- /dev/null
+++ b/tests/roots/test-dummy/future_annotations.rst
@@ -0,0 +1,4 @@
+Dummy Module
+============
+
+.. autofunction:: dummy_module_future_annotations.function_with_py310_annotations
diff --git a/tests/test_sphinx_autodoc_typehints.py b/tests/test_sphinx_autodoc_typehints.py
index 7ef8d73..ca43b71 100644
--- a/tests/test_sphinx_autodoc_typehints.py
+++ b/tests/test_sphinx_autodoc_typehints.py
@@ -6,13 +6,14 @@ import typing
 from typing import (
     IO, Any, AnyStr, Callable, Dict, Generic, Mapping, Match, NewType, Optional, Pattern, Tuple,
     Type, TypeVar, Union)
+from unittest.mock import patch
 
 import pytest
 import typing_extensions
 
 from sphinx_autodoc_typehints import (
     format_annotation, get_annotation_args, get_annotation_class_name, get_annotation_module,
-    process_docstring)
+    normalize_source_lines, process_docstring)
 
 T = TypeVar('T')
 U = TypeVar('U', covariant=True)
@@ -85,6 +86,10 @@ class Metaclass(type):
     pytest.param(A.Inner, __name__, 'A.Inner', (), id='Inner')
 ])
 def test_parse_annotation(annotation, module, class_name, args):
+    if sys.version_info[:2] >= (3, 10) and annotation == W:
+        module = "test_sphinx_autodoc_typehints"
+        class_name = "W"
+        args = ()
     assert get_annotation_module(annotation) == module
     assert get_annotation_class_name(annotation, module) == class_name
     assert get_annotation_args(annotation, module, class_name) == args
@@ -127,7 +132,10 @@ def test_parse_annotation(annotation, module, class_name, args):
                                     ':py:data:`~typing.Any`]',
                  marks=pytest.mark.skipif((3, 5, 0) <= sys.version_info[:3] <= (3, 5, 2),
                                           reason='Union erases the str on 3.5.0 -> 3.5.2')),
-    (Optional[str],                 ':py:data:`~typing.Optional`\\[:py:class:`str`]'),
+    (Optional[str],                 ':py:data:`~typing.Optional`\\' + (
+                                    '[:py:class:`str`]'
+                                    if sys.version_info[:2] < (3, 10) else
+                                    '[:py:class:`str`, :py:obj:`None`]')),
     (Optional[Union[str, bool]],    ':py:data:`~typing.Union`\\[:py:class:`str`, '
                                     ':py:class:`bool`, :py:obj:`None`]'),
     (Callable,                      ':py:data:`~typing.Callable`'),
@@ -151,7 +159,10 @@ def test_parse_annotation(annotation, module, class_name, args):
     (D,                             ':py:class:`~%s.D`' % __name__),
     (E,                             ':py:class:`~%s.E`' % __name__),
     (E[int],                        ':py:class:`~%s.E`\\[:py:class:`int`]' % __name__),
-    (W,                             ':py:func:`~typing.NewType`\\(:py:data:`~W`, :py:class:`str`)')
+    (W,                             ':py:func:`~typing.NewType`\\(:py:data:`~W`, :py:class:`str`)'
+                                    if sys.version_info[:2] < (3, 10) else
+                                    ':py:class:`~test_sphinx_autodoc_typehints.W`'
+     )
 ])
 def test_format_annotation(inv, annotation, expected_result):
     result = format_annotation(annotation)
@@ -223,17 +234,39 @@ def test_process_docstring_slot_wrapper():
     assert not lines
 
 
-@pytest.mark.parametrize('always_document_param_types', [True, False])
-@pytest.mark.sphinx('text', testroot='dummy')
-def test_sphinx_output(app, status, warning, always_document_param_types):
+def set_python_path():
     test_path = pathlib.Path(__file__).parent
 
     # Add test directory to sys.path to allow imports of dummy module.
     if str(test_path) not in sys.path:
         sys.path.insert(0, str(test_path))
 
+
+def maybe_fix_py310(expected_contents):
+    if sys.version_info[:2] >= (3, 10):
+        for old, new in [
+                ("*str** | **None*", '"Optional"["str", "None"]'),
+                ("(*bool*)", '("bool")'),
+                ("(*int*)", '("int")'),
+                ("   str", '   "str"'),
+                ('"Optional"["str"]', '"Optional"["str", "None"]'),
+                ('"Optional"["Callable"[["int", "bytes"], "int"]]',
+                 '"Optional"["Callable"[["int", "bytes"], "int"], "None"]'),
+        ]:
+            expected_contents = expected_contents.replace(old, new)
+    return expected_contents
+
+
+@pytest.mark.parametrize('always_document_param_types', [True, False])
+@pytest.mark.sphinx('text', testroot='dummy')
+@patch('sphinx.writers.text.MAXWIDTH', 2000)
+def test_sphinx_output(app, status, warning, always_document_param_types):
+    set_python_path()
+
     app.config.always_document_param_types = always_document_param_types
     app.config.autodoc_mock_imports = ['mailbox']
+    if sys.version_info < (3, 7):
+        app.config.autodoc_mock_imports.append('dummy_module_future_annotations')
     app.build()
 
     assert 'build succeeded' in status.getvalue()  # Build succeeded
@@ -352,7 +385,7 @@ def test_sphinx_output(app, status, warning, always_document_param_types):
               Return type:
                  "str"
 
-           property a_property
+           property a_property: str
 
               Property docstring
 
@@ -489,8 +522,7 @@ def test_sphinx_output(app, status, warning, always_document_param_types):
               Method docstring.
 
               Parameters:
-                 **x** ("Optional"["Callable"[["int", "bytes"], "int"]]) --
-                 foo
+                 **x** ("Optional"["Callable"[["int", "bytes"], "int"]]) -- foo
 
               Return type:
                  "ClassWithTypehintsNotInline"
@@ -506,9 +538,7 @@ def test_sphinx_output(app, status, warning, always_document_param_types):
 
            Class docstring.{undoc_params_0}
 
-           __init__(x)
-
-              Initialize self.  See help(type(self)) for accurate signature.{undoc_params_1}
+           __init__(x){undoc_params_1}
 
         @dummy_module.Decorator(func)
 
@@ -525,4 +555,56 @@ def test_sphinx_output(app, status, warning, always_document_param_types):
               **x** ("Mailbox") -- function
         ''')
         expected_contents = expected_contents.format(**format_args).replace('–', '--')
-        assert text_contents == expected_contents
+        assert text_contents == maybe_fix_py310(expected_contents)
+
+
+@pytest.mark.skipif(sys.version_info < (3, 7),
+                    reason="Future annotations are not implemented in Python < 3.7")
+@pytest.mark.sphinx('text', testroot='dummy')
+@patch('sphinx.writers.text.MAXWIDTH', 2000)
+def test_sphinx_output_future_annotations(app, status, warning):
+    set_python_path()
+
+    app.config.master_doc = "future_annotations"
+    app.build()
+
+    assert 'build succeeded' in status.getvalue()  # Build succeeded
+
+    text_path = pathlib.Path(app.srcdir) / '_build' / 'text' / 'future_annotations.txt'
+    with text_path.open('r') as f:
+        text_contents = f.read().replace('–', '--')
+        expected_contents = textwrap.dedent('''\
+        Dummy Module
+        ************
+
+        dummy_module_future_annotations.function_with_py310_annotations(self, x, y, z=None)
+
+           Method docstring.
+
+           Parameters:
+              * **x** (*bool*) -- foo
+
+              * **y** (*int*) -- bar
+
+              * **z** (*str** | **None*) -- baz
+
+           Return type:
+              str
+        ''')
+        assert text_contents == maybe_fix_py310(expected_contents)
+
+
+def test_normalize_source_lines_async_def():
+    source = textwrap.dedent("""
+    async def async_function():
+        class InnerClass:
+            def __init__(self): pass
+    """)
+
+    expected = textwrap.dedent("""
+    async def async_function():
+        class InnerClass:
+            def __init__(self): pass
+    """)
+
+    assert normalize_source_lines(source) == expected
diff --git a/tox.ini b/tox.ini
index 54e9bb4..57e4a78 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,6 +9,6 @@ extras = test, type_comments
 commands = python -m pytest {posargs}
 
 [testenv:flake8]
-deps = flake8
-commands = flake8 sphinx_autodoc_typehints.py tests
+deps = pyproject-flake8
+commands = pflake8 sphinx_autodoc_typehints.py tests
 skip_install = true