diff --git a/src/search/base_indexes.py b/src/search/base_indexes.py
index 235f637..5a73182 100644
--- a/src/search/base_indexes.py
+++ b/src/search/base_indexes.py
@@ -77,7 +77,9 @@ class BaseIndex(indexes.SearchIndex):
 
     def prepare_modified_by(self, obj):
         if hasattr(obj, 'modified_by'):
-            return obj.modified_by
+            modified_by = obj.get_modified_by()
+            if modified_by:
+                return modified_by.get_full_name()
         if self.author_obj:
             return self.author_obj.get_full_name()
         return obj.author
--
libgit2 0.21.2