diff --git a/src/govoplan_policy/backend/hierarchy.py b/src/govoplan_policy/backend/hierarchy.py
index 21f20e1..033d975 100644
--- a/src/govoplan_policy/backend/hierarchy.py
+++ b/src/govoplan_policy/backend/hierarchy.py
@@ -66,21 +66,27 @@ def validate_hierarchical_policy_patch(
     relock_message: Callable[[str], str] | None = None,
 ) -> tuple[PolicyValidationIssue, ...]:
     issues: list[PolicyValidationIssue] = []
-    lock_message = locked_field_message or (lambda field: f"{field} is locked by the parent policy.")
-    reenable_message = relock_message or (lambda field: f"{field} limiting cannot be re-enabled below a parent policy lock.")
+    lock_message = locked_field_message or (lambda field_name: f"{field_name} is locked by the parent policy.")
+    reenable_message = relock_message or (
+        lambda field_name: f"{field_name} limiting cannot be re-enabled below a parent policy lock."
+    )
 
-    for field in field_keys:
-        if field in patch and patch.get(field) is not None and not parent_allow_lower_level_limits.get(field, True):
+    for field_name in field_keys:
+        if (
+            field_name in patch
+            and patch.get(field_name) is not None
+            and not parent_allow_lower_level_limits.get(field_name, True)
+        ):
             issues.append(PolicyValidationIssue(
                 code="field_locked_by_parent",
-                field=field,
-                message=lock_message(field),
+                field=field_name,
+                message=lock_message(field_name),
             ))
 
     patch_allow = patch.get("allow_lower_level_limits")
     if isinstance(patch_allow, Mapping):
-        for field, allowed in patch_allow.items():
-            clean_field = str(field)
+        for field_name, allowed in patch_allow.items():
+            clean_field = str(field_name)
             if bool(allowed) and not parent_allow_lower_level_limits.get(clean_field, True):
                 issues.append(PolicyValidationIssue(
                     code="lower_level_limit_locked_by_parent",
@@ -125,9 +131,9 @@ def simulate_hierarchical_policy_change(
         relock_message=relock_message,
     )
     changed_fields = tuple(
-        field
-        for field in (*field_keys, "allow_lower_level_limits")
-        if field in patch and current_policy.get(field) != patch.get(field)
+        field_name
+        for field_name in (*field_keys, "allow_lower_level_limits")
+        if field_name in patch and current_policy.get(field_name) != patch.get(field_name)
     )
     allowed = not any(issue.severity == "blocker" for issue in issues)
     decision = PolicyDecision(