diff --git a/invenio_oaiserver/verbs.py b/invenio_oaiserver/verbs.py
index 563a36b..7461536 100644
--- a/invenio_oaiserver/verbs.py
+++ b/invenio_oaiserver/verbs.py
@@ -91,8 +91,8 @@ def validate(self, data, **kwargs):
                 data['from_'] > data['until']:
             raise ValidationError('Date "from" must be before "until".')
         extra = set(request.values.keys()) - set([
-            getattr(f, 'load_from', None) or getattr(
-                f, 'data_key', None) or f.name for f in self.fields.values()
+            f.metadata.get('load_from', None) or f.metadata
+                .get('data_key', None) or f.name for f in self.fields.values()
         ])
         if extra:
             raise ValidationError('You have passed too many arguments.')