diff --git a/product/ERP5/Tool/NotificationTool.py b/product/ERP5/Tool/NotificationTool.py
index 1cd95005a65595a319ee022044b5fd4c821215ee..7fe87cb77997c350592a27fa6a939c43ca924da7 100644
--- a/product/ERP5/Tool/NotificationTool.py
+++ b/product/ERP5/Tool/NotificationTool.py
@@ -182,7 +182,7 @@ class NotificationTool(BaseTool):
       email_from_address = default_email
 
     # To is a list - let us find all members
-    if isinstance(recipient, basestring):
+    if not isinstance(recipient, (list, tuple)):
       recipient = (recipient, )
 
     # If no recipient is defined, just send an email to the