diff --git a/src/azul/plugins/metadata/anvil/__init__.py b/src/azul/plugins/metadata/anvil/__init__.py
index aed275cad..02df4f6a3 100644
--- a/src/azul/plugins/metadata/anvil/__init__.py
+++ b/src/azul/plugins/metadata/anvil/__init__.py
@@ -222,7 +222,9 @@ def _field_mapping(self) -> MetadataPlugin._FieldMapping:
                         ]
                     },
                     # These field names are hard-coded in the implementation of
-                    # the repository service/controller.
+                    # the repository service/controller. Also, these field paths
+                    # have a brittle coupling that must be maintained to the
+                    # field lookups in `self.manifest_config`.
                     **{
                         # Not in schema
                         'version': 'fileVersion',
@@ -273,14 +275,12 @@ def facets(self) -> Sequence[str]:
     def manifest_config(self) -> ManifestConfig:
         result = defaultdict(dict)
 
-        # This is used to modify the field names from how they are specified in
-        # the field mapping. Keys are field paths in an ES hit, and values are
-        # the desired manifest column name, or None to omit the column from the
-        # manifest.
-        custom_field_names = {
-            ('contents', 'files', 'uuid'): None,
-            ('contents', 'files', 'version'): None,
-        }
+        # Note that there is a brittle coupling that must be maintained between
+        # the fields listed here and those used in `self._field_mapping`.
+        fields_to_omit_from_manifest = [
+            ('contents', 'files', 'uuid'),
+            ('contents', 'files', 'version'),
+        ]
 
         def recurse(mapping: MetadataPlugin._FieldMapping, path: FieldPath):
             for path_element, name_or_type in mapping.items():
@@ -290,15 +290,16 @@ def recurse(mapping: MetadataPlugin._FieldMapping, path: FieldPath):
                 elif isinstance(name_or_type, str):
                     if new_path == ('entity_id',):
                         pass
-                    elif new_path in custom_field_names:
-                        result[path][path_element] = custom_field_names.pop(new_path)
+                    elif new_path in fields_to_omit_from_manifest:
+                        result[path][path_element] = None
+                        fields_to_omit_from_manifest.remove(new_path)
                     else:
                         result[path][path_element] = name_or_type
                 else:
                     assert False, (path, path_element, name_or_type)
 
         recurse(self._field_mapping, ())
-        assert len(custom_field_names) == 0, custom_field_names
+        assert len(fields_to_omit_from_manifest) == 0, fields_to_omit_from_manifest
         # The file URL is synthesized from the `uuid` and `version` fields.
         # Above, we already configured these two fields to be omitted from the
         # manifest since they are not informative to the user.