diff --git a/dev/treefmt.nix b/dev/treefmt.nix
index 2181222..e2aa08b 100644
--- a/dev/treefmt.nix
+++ b/dev/treefmt.nix
@@ -66,7 +66,7 @@
       options = [
         "-eucx"
         ''
-          ${pkgs.lib.getExe pkgs.ruff} --fix "$@"
+          ${pkgs.lib.getExe pkgs.ruff} check --fix "$@"
           ${pkgs.lib.getExe pkgs.ruff} format "$@"
         ''
         "--" # this argument is ignored by bash
diff --git a/pyproject.toml b/pyproject.toml
index cf90945..78506d8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,7 @@
 [tool.ruff]
 line-length = 88
 
+[tool.ruff.lint]
 select = ["E", "F", "I"]
 ignore = [ "E501" ]