diff --git a/2021/Makefile b/2021/Makefile
index da34a7c..57c8862 100644
--- a/2021/Makefile
+++ b/2021/Makefile
@@ -37,7 +37,7 @@ lint-types:
 
 .PHONY: format
 format:
-	$(ruff) --fix-only $(srcs)
+	$(ruff) check --fix-only $(srcs)
 	$(black) $(srcs)
 
 .PHONY: distclean
diff --git a/2021/ruff.toml b/2021/ruff.toml
index cd24234..eee877d 100644
--- a/2021/ruff.toml
+++ b/2021/ruff.toml
@@ -1,3 +1,10 @@
+# Group errors by file.
+output-format = "full"
+
+# Show sumamry of fixes.
+show-fixes = true
+
+[lint]
 extend-select = [
     "W", # pycodestyle warnings
     "I", # isort
@@ -5,16 +12,7 @@ extend-select = [
     "B", # flake8-bugbear
 ]
 
-# Group errors by file.
-output-format = "grouped"
-
-# Show source context of error.
-show-source = true
-
-# Show sumamry of fixes.
-show-fixes = true
-
-[isort]
+[lint.isort]
 force-single-line = true
 force-sort-within-sections = true
 order-by-type = false