diff --git a/core/search_indexes.py b/core/search_indexes.py
index 23879144..03ececa4 100644
--- a/core/search_indexes.py
+++ b/core/search_indexes.py
@@ -13,3 +13,5 @@ class UserIndex(indexes.SearchIndex, indexes.Indexable):
         """Used when the entire index for model is updated."""
         return self.get_model().objects.all()
 
+    def get_updated_field(self):
+        return "last_update"