diff --git a/pyproject.toml b/pyproject.toml
index 64ec8c6..bbdf9a5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -62,9 +62,15 @@ test = [
 
 [tool.ruff]
 line-length = 180
-lint.ignore = ["E722"]
 exclude = ["scratch"]
 
+[tool.ruff.lint]
+# Pin the rule set to the classic ruff default (pyflakes + pycodestyle
+# errors) so `ruff check` stays deterministic as new ruff versions widen
+# their defaults. E722 (bare except) is used intentionally in a few places.
+select = ["E4", "E7", "E9", "F"]
+ignore = ["E722"]
+
 [build-system]
 requires = ["setuptools>=43.0.0", "wheel"]
 build-backend = "setuptools.build_meta"