diff --git a/product/ERP5Security/ERP5GroupManager.py b/product/ERP5Security/ERP5GroupManager.py
index 46827c071dd75c661795f0c956899ad78d6f944f..49b2a4d05524eac5b95416e7bc88d35b10290440 100644
--- a/product/ERP5Security/ERP5GroupManager.py
+++ b/product/ERP5Security/ERP5GroupManager.py
@@ -139,6 +139,10 @@ class ERP5GroupManager(BasePlugin):
           security_category_list = security_category_dict.setdefault(
                                             base_category_list, [])
           try:
+            # The called script may want to distinguish if it is called
+            # from here or from _updateLocalRolesOnSecurityGroups.
+            # Currently, passing portal_type='' (instead of 'Person')
+            # is the only way to make the difference.
             security_category_list.extend(
               method(base_category_list, user_name, person_object, '')
             )