diff --git a/ruff.toml b/ruff.toml
index 41d3dc5b..069aa279 100644
--- a/ruff.toml
+++ b/ruff.toml
@@ -6,6 +6,5 @@ lint.select = [
     "S307",  # suspicious-eval-usage
     "F401",  # unused-import
     "F841",  # unused-local-variable
-    # TODO: Enable F821 after all errors has been fixed. Remaining errors: 7.
-    # "F821",  # undefined-name
+    "F821",  # undefined-name
 ]
\ No newline at end of file