diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 50c073a0..24b155d3 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -13,7 +13,7 @@ repos:
           - id: black
 
     - repo: https://github.com/PyCQA/autoflake
-      rev: v2.0.1
+      rev: v2.0.2
       hooks:
           - id: autoflake
 
@@ -34,7 +34,7 @@ repos:
           - id: mypy
 
     - repo: https://github.com/RobertCraigie/pyright-python
-      rev: v1.1.298
+      rev: v1.1.299
       hooks:
           - id: pyright
             entry: env PYRIGHT_PYTHON_FORCE_VERSION=latest pyright
@@ -109,7 +109,7 @@ repos:
           - id: yamlfmt
 
     - repo: https://github.com/macisamuele/language-formatters-pre-commit-hooks
-      rev: v2.7.0
+      rev: v2.8.0
       hooks:
           - id: pretty-format-toml
             args: [--autofix]
diff --git a/.pre-commit-hooks.yaml b/.pre-commit-hooks.yaml
new file mode 100644
index 00000000..aba3df0e
--- /dev/null
+++ b/.pre-commit-hooks.yaml
@@ -0,0 +1,6 @@
+---
+    - id: flake8_trio
+      name: flake8_trio
+      entry: flake8_trio
+      language: python
+      types: [python]
diff --git a/flake8_trio/__init__.py b/flake8_trio/__init__.py
index 8091c281..7d51cbd7 100644
--- a/flake8_trio/__init__.py
+++ b/flake8_trio/__init__.py
@@ -74,7 +74,7 @@ def cst_parse_module_native(source: str) -> cst.Module:
     return mod
 
 
-def main():
+def main() -> int:
     parser = ArgumentParser(prog="flake8_trio")
     parser.add_argument(
         nargs="*",
@@ -105,17 +105,20 @@ def main():
                 "Doesn't seem to be a git repo; pass filenames to format.",
                 file=sys.stderr,
             )
-            sys.exit(1)
+            return 1
         all_filenames = [
             os.path.join(root, f) for f in all_filenames if _should_format(f)
         ]
+    any_error = False
     for file in all_filenames:
         plugin = Plugin.from_filename(file)
         for error in sorted(plugin.run()):
             print(f"{file}:{error}")
+            any_error = True
         if plugin.options.autofix:
             with open(file, "w") as file:
                 file.write(plugin.module.code)
+    return 1 if any_error else 0
 
 
 class Plugin:
diff --git a/flake8_trio/__main__.py b/flake8_trio/__main__.py
index 393c2c0b..4f399f5b 100644
--- a/flake8_trio/__main__.py
+++ b/flake8_trio/__main__.py
@@ -1,4 +1,6 @@
 """Entry file when executed with `python -m`."""
+import sys
+
 from . import main
 
-main()
+sys.exit(main())
diff --git a/setup.py b/setup.py
index 3a27e8f1..7213c483 100755
--- a/setup.py
+++ b/setup.py
@@ -29,7 +29,7 @@ def local_file(name: str) -> Path:
     license="MIT",
     description="A highly opinionated flake8 plugin for Trio-related problems.",
     zip_safe=False,
-    install_requires=["flake8"],
+    install_requires=["flake8", "libcst"],
     python_requires=">=3.9",
     classifiers=[
         "Development Status :: 3 - Alpha",
diff --git a/tests/test_config_and_args.py b/tests/test_config_and_args.py
index 4f3c32d1..da59a621 100644
--- a/tests/test_config_and_args.py
+++ b/tests/test_config_and_args.py
@@ -8,7 +8,7 @@
 
 import pytest
 
-from flake8_trio import Plugin
+from flake8_trio import Plugin, main
 
 from .test_flake8_trio import initialize_options
 
@@ -36,10 +36,44 @@ def test_run_flake8_trio(tmp_path: Path):
         cwd=tmp_path,
         capture_output=True,
     )
+    assert res.returncode == 1
     assert not res.stderr
     assert res.stdout == err_msg.encode("ascii")
 
 
+def test_systemexit_0(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+):
+    monkeypatch.chdir(tmp_path)
+    monkeypatch.setattr(sys, "argv", [tmp_path / "flake8_trio", "./example.py"])
+
+    tmp_path.joinpath("example.py").write_text("")
+
+    with pytest.raises(SystemExit) as exc_info:
+        from flake8_trio import __main__  # noqa
+
+    assert exc_info.value.code == 0
+    out, err = capsys.readouterr()
+    assert not out
+    assert not err
+
+
+def test_systemexit_1(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+):
+    err_msg = _common_error_setup(tmp_path)
+    monkeypatch.chdir(tmp_path)
+    monkeypatch.setattr(sys, "argv", [tmp_path / "flake8_trio", "./example.py"])
+
+    with pytest.raises(SystemExit) as exc_info:
+        from flake8_trio import __main__  # noqa
+
+    assert exc_info.value.code == 1
+    out, err = capsys.readouterr()
+    assert out == err_msg
+    assert not err
+
+
 def test_run_in_git_repo(tmp_path: Path):
     err_msg = _common_error_setup(tmp_path)
     assert subprocess.run(["git", "init"], cwd=tmp_path, capture_output=True)
@@ -51,6 +85,7 @@ def test_run_in_git_repo(tmp_path: Path):
         cwd=tmp_path,
         capture_output=True,
     )
+    assert res.returncode == 1
     assert not res.stderr
     assert res.stdout == err_msg.encode("ascii")
 
@@ -60,8 +95,7 @@ def test_run_no_git_repo(
 ):
     monkeypatch.chdir(tmp_path)
     monkeypatch.setattr(sys, "argv", [tmp_path / "flake8_trio"])
-    with pytest.raises(SystemExit):
-        from flake8_trio import __main__  # noqa
+    assert main() == 1
     out, err = capsys.readouterr()
     assert err == "Doesn't seem to be a git repo; pass filenames to format.\n"
     assert not out
@@ -75,7 +109,7 @@ def test_run_100_autofix(
     monkeypatch.setattr(
         sys, "argv", [tmp_path / "flake8_trio", "--autofix", "./example.py"]
     )
-    from flake8_trio import __main__  # noqa
+    assert main() == 1
 
     out, err = capsys.readouterr()
     assert out == err_msg
@@ -189,6 +223,7 @@ def test_200_from_config_flake8_internals(
 def test_200_from_config_subprocess(tmp_path: Path):
     err_msg = _test_trio200_from_config_common(tmp_path)
     res = subprocess.run(["flake8"], cwd=tmp_path, capture_output=True)
+    assert res.returncode == 1
     assert not res.stderr
     assert res.stdout == err_msg.encode("ascii")