diff --git a/product/ERP5/Document/BusinessTemplate.py b/product/ERP5/Document/BusinessTemplate.py
index d3b333f10e3c92597061c906d5116e3cfc5a50da..ecce6169f3c2fe10c6b919a18a10dfa84611e731 100644
--- a/product/ERP5/Document/BusinessTemplate.py
+++ b/product/ERP5/Document/BusinessTemplate.py
@@ -4557,6 +4557,7 @@ Business Template is a set of definitions, such as skins, portal types and categ
 
       # remove object from old business template
       if len(remove_object_dict):
+        # XXX: this code assumes that there is an installed_bt
         for item_name in installed_bt._item_name_list:
           item = getattr(installed_bt, item_name, None)
           if item is not None: