diff --git a/h11/_connection.py b/h11/_connection.py
index a812298..e37d82a 100644
--- a/h11/_connection.py
+++ b/h11/_connection.py
@@ -428,7 +428,7 @@ def _extract_next_receive_event(
                 # return that event, and then the state will change and we'll
                 # get called again to generate the actual ConnectionClosed().
                 if hasattr(self._reader, "read_eof"):
-                    event = self._reader.read_eof()  # type: ignore[attr-defined]
+                    event = self._reader.read_eof()
                 else:
                     event = ConnectionClosed()
         if event is None:
@@ -505,7 +505,13 @@ def send(self, event: ConnectionClosed) -> None:
         ...
 
     @overload
-    def send(self, event: Event) -> bytes:
+    def send(
+        self, event: Union[Request, InformationalResponse, Response, Data, EndOfMessage]
+    ) -> bytes:
+        ...
+
+    @overload
+    def send(self, event: Event) -> Optional[bytes]:
         ...
 
     def send(self, event: Event) -> Optional[bytes]:
diff --git a/h11/_events.py b/h11/_events.py
index 075bf8a..ca1c3ad 100644
--- a/h11/_events.py
+++ b/h11/_events.py
@@ -7,8 +7,8 @@
 
 import re
 from abc import ABC
-from dataclasses import dataclass, field
-from typing import Any, cast, Dict, List, Tuple, Union
+from dataclasses import dataclass
+from typing import List, Tuple, Union
 
 from ._abnf import method, request_target
 from ._headers import Headers, normalize_and_validate
diff --git a/h11/tests/test_against_stdlib_http.py b/h11/tests/test_against_stdlib_http.py
index f0eff63..3f66a10 100644
--- a/h11/tests/test_against_stdlib_http.py
+++ b/h11/tests/test_against_stdlib_http.py
@@ -13,7 +13,7 @@
 
 @contextmanager
 def socket_server(
-    handler: Callable[..., socketserver.BaseRequestHandler]
+    handler: Callable[..., socketserver.BaseRequestHandler],
 ) -> Generator[socketserver.TCPServer, None, None]:
     httpd = socketserver.TCPServer(("127.0.0.1", 0), handler)
     thread = threading.Thread(
@@ -39,17 +39,17 @@ def translate_path(self, path: str) -> str:
 
 def test_h11_as_client() -> None:
     with socket_server(SingleMindedRequestHandler) as httpd:
-        with closing(socket.create_connection(httpd.server_address)) as s:
+        with closing(socket.create_connection(httpd.server_address)) as s:  # type: ignore[arg-type]
             c = h11.Connection(h11.CLIENT)
 
             s.sendall(
-                c.send(  # type: ignore[arg-type]
+                c.send(
                     h11.Request(
                         method="GET", target="/foo", headers=[("Host", "localhost")]
                     )
                 )
             )
-            s.sendall(c.send(h11.EndOfMessage()))  # type: ignore[arg-type]
+            s.sendall(c.send(h11.EndOfMessage()))
 
             data = bytearray()
             while True:
@@ -96,7 +96,7 @@ def handle(self) -> None:
                     },
                 }
             )
-            s.sendall(c.send(h11.Response(status_code=200, headers=[])))  # type: ignore[arg-type]
+            s.sendall(c.send(h11.Response(status_code=200, headers=[])))
             s.sendall(c.send(h11.Data(data=info.encode("ascii"))))
             s.sendall(c.send(h11.EndOfMessage()))
 
@@ -104,7 +104,7 @@ def handle(self) -> None:
 def test_h11_as_server() -> None:
     with socket_server(H11RequestHandler) as httpd:
         host, port = httpd.server_address
-        url = f"http://{host}:{port}/some-path"
+        url = f"http://{host}:{port}/some-path"  # type: ignore[str-bytes-safe]
         with closing(urlopen(url)) as f:
             assert f.getcode() == 200
             data = f.read()
diff --git a/h11/tests/test_connection.py b/h11/tests/test_connection.py
index f45cb97..01260dc 100644
--- a/h11/tests/test_connection.py
+++ b/h11/tests/test_connection.py
@@ -7,7 +7,6 @@
     ConnectionClosed,
     Data,
     EndOfMessage,
-    Event,
     InformationalResponse,
     Request,
     Response,
@@ -17,7 +16,6 @@
     CLOSED,
     DONE,
     ERROR,
-    IDLE,
     MIGHT_SWITCH_PROTOCOL,
     MUST_CLOSE,
     SEND_BODY,
@@ -48,15 +46,15 @@ def test__keep_alive() -> None:
         )
     )
     assert not _keep_alive(
-        Request(method="GET", target="/", headers=[], http_version="1.0")  # type: ignore[arg-type]
+        Request(method="GET", target="/", headers=[], http_version="1.0")
     )
 
-    assert _keep_alive(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    assert _keep_alive(Response(status_code=200, headers=[]))
     assert not _keep_alive(Response(status_code=200, headers=[("Connection", "close")]))
     assert not _keep_alive(
         Response(status_code=200, headers=[("Connection", "a, b, cLOse, foo")])
     )
-    assert not _keep_alive(Response(status_code=200, headers=[], http_version="1.0"))  # type: ignore[arg-type]
+    assert not _keep_alive(Response(status_code=200, headers=[], http_version="1.0"))
 
 
 def test__body_framing() -> None:
@@ -135,7 +133,7 @@ def test_Connection_basics_and_content_length() -> None:
     assert p.conn[CLIENT].their_http_version is None
     assert p.conn[SERVER].their_http_version == b"1.1"
 
-    data = p.send(SERVER, InformationalResponse(status_code=100, headers=[]))  # type: ignore[arg-type]
+    data = p.send(SERVER, InformationalResponse(status_code=100, headers=[]))
     assert data == b"HTTP/1.1 100 \r\n\r\n"
 
     data = p.send(SERVER, Response(status_code=200, headers=[("Content-Length", "11")]))
@@ -247,7 +245,7 @@ def test_client_talking_to_http10_server() -> None:
     assert c.our_state is DONE
     # No content-length, so Http10 framing for body
     assert receive_and_get(c, b"HTTP/1.0 200 OK\r\n\r\n") == [
-        Response(status_code=200, headers=[], http_version="1.0", reason=b"OK")  # type: ignore[arg-type]
+        Response(status_code=200, headers=[], http_version="1.0", reason=b"OK")
     ]
     assert c.our_state is MUST_CLOSE
     assert receive_and_get(c, b"12345") == [Data(data=b"12345")]
@@ -261,14 +259,14 @@ def test_server_talking_to_http10_client() -> None:
     # No content-length, so no body
     # NB: no host header
     assert receive_and_get(c, b"GET / HTTP/1.0\r\n\r\n") == [
-        Request(method="GET", target="/", headers=[], http_version="1.0"),  # type: ignore[arg-type]
+        Request(method="GET", target="/", headers=[], http_version="1.0"),
         EndOfMessage(),
     ]
     assert c.their_state is MUST_CLOSE
 
     # We automatically Connection: close back at them
     assert (
-        c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+        c.send(Response(status_code=200, headers=[]))
         == b"HTTP/1.1 200 \r\nConnection: close\r\n\r\n"
     )
 
@@ -356,7 +354,7 @@ def test_automagic_connection_close_handling() -> None:
     p.send(
         SERVER,
         # no header here...
-        [Response(status_code=204, headers=[]), EndOfMessage()],  # type: ignore[arg-type]
+        [Response(status_code=204, headers=[]), EndOfMessage()],
         # ...but oh look, it arrived anyway
         expect=[
             Response(status_code=204, headers=[("connection", "close")]),
@@ -390,7 +388,7 @@ def setup() -> ConnectionPair:
 
     # Disabled by 100 Continue
     p = setup()
-    p.send(SERVER, InformationalResponse(status_code=100, headers=[]))  # type: ignore[arg-type]
+    p.send(SERVER, InformationalResponse(status_code=100, headers=[]))
     for conn in p.conns:
         assert not conn.client_is_waiting_for_100_continue
         assert not conn.they_are_waiting_for_100_continue
@@ -471,7 +469,7 @@ def test_max_incomplete_event_size_countermeasure() -> None:
     # Even more data comes in, still no problem
     c.receive_data(b"X" * 1000)
     # We can respond and reuse to get the second pipelined request
-    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(Response(status_code=200, headers=[]))
     c.send(EndOfMessage())
     c.start_next_cycle()
     assert get_all_events(c) == [
@@ -481,7 +479,7 @@ def test_max_incomplete_event_size_countermeasure() -> None:
     # But once we unpause and try to read the next message, and find that it's
     # incomplete and the buffer is *still* way too large, then *that's* a
     # problem:
-    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(Response(status_code=200, headers=[]))
     c.send(EndOfMessage())
     c.start_next_cycle()
     with pytest.raises(RemoteProtocolError):
@@ -547,7 +545,7 @@ def test_pipelining() -> None:
 
     assert c.next_event() is PAUSED
 
-    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(Response(status_code=200, headers=[]))
     c.send(EndOfMessage())
     assert c.their_state is DONE
     assert c.our_state is DONE
@@ -564,7 +562,7 @@ def test_pipelining() -> None:
         EndOfMessage(),
     ]
     assert c.next_event() is PAUSED
-    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(Response(status_code=200, headers=[]))
     c.send(EndOfMessage())
     c.start_next_cycle()
 
@@ -574,7 +572,7 @@ def test_pipelining() -> None:
     ]
     # Doesn't pause this time, no trailing data
     assert c.next_event() is NEED_DATA
-    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(Response(status_code=200, headers=[]))
     c.send(EndOfMessage())
 
     # Arrival of more data triggers pause
@@ -683,7 +681,7 @@ def setup() -> ConnectionPair:
         sc.send(EndOfMessage())
         sc.start_next_cycle()
         assert get_all_events(sc) == [
-            Request(method="GET", target="/", headers=[], http_version="1.0"),  # type: ignore[arg-type]
+            Request(method="GET", target="/", headers=[], http_version="1.0"),
             EndOfMessage(),
         ]
 
@@ -845,7 +843,7 @@ def test_pipelined_close() -> None:
         EndOfMessage(),
     ]
     assert c.states[CLIENT] is DONE
-    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(Response(status_code=200, headers=[]))
     c.send(EndOfMessage())
     assert c.states[SERVER] is DONE
     c.start_next_cycle()
@@ -860,7 +858,7 @@ def test_pipelined_close() -> None:
         ConnectionClosed(),
     ]
     assert c.states == {CLIENT: CLOSED, SERVER: SEND_RESPONSE}
-    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(Response(status_code=200, headers=[]))
     c.send(EndOfMessage())
     assert c.states == {CLIENT: CLOSED, SERVER: MUST_CLOSE}
     c.send(ConnectionClosed())
@@ -919,7 +917,7 @@ def test_errors() -> None:
         # But we can still yell at the client for sending us gibberish
         if role is SERVER:
             assert (
-                c.send(Response(status_code=400, headers=[]))  # type: ignore[arg-type]
+                c.send(Response(status_code=400, headers=[]))
                 == b"HTTP/1.1 400 \r\nConnection: close\r\n\r\n"
             )
 
@@ -946,8 +944,8 @@ def conn(role: Type[Sentinel]) -> Connection:
                 http_version="1.0",
             )
         elif role is SERVER:
-            good = Response(status_code=200, headers=[])  # type: ignore[arg-type,assignment]
-            bad = Response(status_code=200, headers=[], http_version="1.0")  # type: ignore[arg-type,assignment]
+            good = Response(status_code=200, headers=[])  # type: ignore[assignment]
+            bad = Response(status_code=200, headers=[], http_version="1.0")  # type: ignore[assignment]
         # Make sure 'good' actually is good
         c = conn(role)
         c.send(good)
@@ -1063,14 +1061,14 @@ def setup(method: bytes, http_version: bytes) -> Connection:
         # No Content-Length, HTTP/1.1 peer, should use chunked
         c = setup(method, b"1.1")
         assert (
-            c.send(Response(status_code=200, headers=[])) == b"HTTP/1.1 200 \r\n"  # type: ignore[arg-type]
+            c.send(Response(status_code=200, headers=[])) == b"HTTP/1.1 200 \r\n"
             b"Transfer-Encoding: chunked\r\n\r\n"
         )
 
         # No Content-Length, HTTP/1.0 peer, frame with connection: close
         c = setup(method, b"1.0")
         assert (
-            c.send(Response(status_code=200, headers=[])) == b"HTTP/1.1 200 \r\n"  # type: ignore[arg-type]
+            c.send(Response(status_code=200, headers=[])) == b"HTTP/1.1 200 \r\n"
             b"Connection: close\r\n\r\n"
         )
 
diff --git a/h11/tests/test_events.py b/h11/tests/test_events.py
index bc6c313..d691545 100644
--- a/h11/tests/test_events.py
+++ b/h11/tests/test_events.py
@@ -2,12 +2,10 @@
 
 import pytest
 
-from .. import _events
 from .._events import (
     ConnectionClosed,
     Data,
     EndOfMessage,
-    Event,
     InformationalResponse,
     Request,
     Response,
@@ -101,13 +99,13 @@ def test_events() -> None:
     with pytest.raises(LocalProtocolError):
         InformationalResponse(status_code=200, headers=[("Host", "a")])
 
-    resp = Response(status_code=204, headers=[], http_version="1.0")  # type: ignore[arg-type]
+    resp = Response(status_code=204, headers=[], http_version="1.0")
     assert resp.status_code == 204
     assert resp.headers == []
     assert resp.http_version == b"1.0"
 
     with pytest.raises(LocalProtocolError):
-        resp = Response(status_code=100, headers=[], http_version="1.0")  # type: ignore[arg-type]
+        resp = Response(status_code=100, headers=[], http_version="1.0")
 
     with pytest.raises(LocalProtocolError):
         Response(status_code="100", headers=[], http_version="1.0")  # type: ignore[arg-type]
@@ -128,7 +126,7 @@ def test_events() -> None:
 def test_intenum_status_code() -> None:
     # https://github.com/python-hyper/h11/issues/72
 
-    r = Response(status_code=HTTPStatus.OK, headers=[], http_version="1.0")  # type: ignore[arg-type]
+    r = Response(status_code=HTTPStatus.OK, headers=[], http_version="1.0")
     assert r.status_code == HTTPStatus.OK
     assert type(r.status_code) is not type(HTTPStatus.OK)
     assert type(r.status_code) is int
diff --git a/h11/tests/test_helpers.py b/h11/tests/test_helpers.py
index c329c76..9a30dc6 100644
--- a/h11/tests/test_helpers.py
+++ b/h11/tests/test_helpers.py
@@ -1,12 +1,4 @@
-from .._events import (
-    ConnectionClosed,
-    Data,
-    EndOfMessage,
-    Event,
-    InformationalResponse,
-    Request,
-    Response,
-)
+from .._events import Data, EndOfMessage, Response
 from .helpers import normalize_data_events
 
 
@@ -15,7 +7,7 @@ def test_normalize_data_events() -> None:
         [
             Data(data=bytearray(b"1")),
             Data(data=b"2"),
-            Response(status_code=200, headers=[]),  # type: ignore[arg-type]
+            Response(status_code=200, headers=[]),
             Data(data=b"3"),
             Data(data=b"4"),
             EndOfMessage(),
@@ -25,7 +17,7 @@ def test_normalize_data_events() -> None:
         ]
     ) == [
         Data(data=b"12"),
-        Response(status_code=200, headers=[]),  # type: ignore[arg-type]
+        Response(status_code=200, headers=[]),
         Data(data=b"34"),
         EndOfMessage(),
         Data(data=b"567"),
diff --git a/h11/tests/test_io.py b/h11/tests/test_io.py
index 2874122..42137b0 100644
--- a/h11/tests/test_io.py
+++ b/h11/tests/test_io.py
@@ -3,7 +3,6 @@
 import pytest
 
 from .._events import (
-    ConnectionClosed,
     Data,
     EndOfMessage,
     Event,
@@ -20,18 +19,7 @@
     READERS,
 )
 from .._receivebuffer import ReceiveBuffer
-from .._state import (
-    CLIENT,
-    CLOSED,
-    DONE,
-    IDLE,
-    MIGHT_SWITCH_PROTOCOL,
-    MUST_CLOSE,
-    SEND_BODY,
-    SEND_RESPONSE,
-    SERVER,
-    SWITCHED_PROTOCOL,
-)
+from .._state import CLIENT, IDLE, SEND_RESPONSE, SERVER
 from .._util import LocalProtocolError
 from .._writers import (
     ChunkedWriter,
@@ -61,7 +49,7 @@
     ),
     (
         (SERVER, SEND_RESPONSE),
-        Response(status_code=200, headers=[], reason=b"OK"),  # type: ignore[arg-type]
+        Response(status_code=200, headers=[], reason=b"OK"),
         b"HTTP/1.1 200 OK\r\n\r\n",
     ),
     (
@@ -73,7 +61,7 @@
     ),
     (
         (SERVER, SEND_RESPONSE),
-        InformationalResponse(status_code=101, headers=[], reason=b"Upgrade"),  # type: ignore[arg-type]
+        InformationalResponse(status_code=101, headers=[], reason=b"Upgrade"),
         b"HTTP/1.1 101 Upgrade\r\n\r\n",
     ),
 ]
@@ -182,7 +170,7 @@ def test_readers_unusual() -> None:
     tr(
         READERS[CLIENT, IDLE],
         b"HEAD /foo HTTP/1.0\r\n\r\n",
-        Request(method="HEAD", target="/foo", headers=[], http_version="1.0"),  # type: ignore[arg-type]
+        Request(method="HEAD", target="/foo", headers=[], http_version="1.0"),
     )
 
     tr(
diff --git a/pyproject.toml b/pyproject.toml
index edd11ae..64a6883 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -38,3 +38,9 @@ showcontent = true
 directory = "misc"
 name = "Miscellaneous internal changes"
 showcontent = true
+
+[tool.mypy]
+strict = true
+warn_unused_configs = true
+warn_unused_ignores = true
+show_error_codes = true
diff --git a/setup.cfg b/setup.cfg
deleted file mode 100644
index 85dcc1f..0000000
--- a/setup.cfg
+++ /dev/null
@@ -1,5 +0,0 @@
-[mypy]
-strict = true
-warn_unused_configs = true
-warn_unused_ignores = true
-show_error_codes = true
diff --git a/tox.ini b/tox.ini
index 8394aa1..a28db7d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,10 +3,10 @@ envlist = format, py{38, 39, 310, 311, 312, py3}, mypy
 
 [gh-actions]
 python =
-    3.8: py38
+    3.8: py38, format, mypy
     3.9: py39
     3.10: py310
-    3.11: py311, format, mypy
+    3.11: py311
     3.12: py312
     pypy-3.9: pypy3
     pypy-3.10: pypy3
@@ -16,7 +16,7 @@ deps = -r{toxinidir}/test-requirements.txt
 commands = pytest --cov=h11 --cov-config=.coveragerc h11
 
 [testenv:format]
-basepython = python3.10
+basepython = python3.8
 deps = -r{toxinidir}/format-requirements.txt
 commands =
     black --check --diff h11/ bench/ examples/ fuzz/
@@ -25,7 +25,7 @@ commands =
 [testenv:mypy]
 basepython = python3.8
 deps =
-    mypy
+    mypy==1.8.0
     pytest
 commands =
     mypy h11/