diff --git a/product/ERP5/Document/BusinessTemplate.py b/product/ERP5/Document/BusinessTemplate.py
index ddb7910ef6bb7f05d3fee5a588563858472645a9..004fa2823e6fd4bf4c97a89cb6fc2f46c9733688 100644
--- a/product/ERP5/Document/BusinessTemplate.py
+++ b/product/ERP5/Document/BusinessTemplate.py
@@ -6950,6 +6950,8 @@ Business Template is a set of definitions, such as skins, portal types and categ
                     mixin_class_name = m.__name__
 
               if mixin_class_name is None:
+                LOG("BusinessTemplate", WARNING,
+                    "%s: No mixin class defined or incorrectly named?" % filepath)
                 continue
 
               subsubmodule_name = mixin_class_name