diff --git a/addons/plugin/plugin_handler.py b/addons/plugin/plugin_handler.py
index e7e8b9ea817..3c322b67bf4 100644
--- a/addons/plugin/plugin_handler.py
+++ b/addons/plugin/plugin_handler.py
@@ -92,6 +92,8 @@ class plugin_handler(osv.osv_memory):
         msg = mail_message.parse_message(email)
         message_id = msg.get('message-id')
         mail_ids = mail_message.search(cr, uid, [('message_id','=',message_id),('res_id','=',res_id),('model','=',model)])
+        if model=='res.partner':
+            model_obj = self.pool.get('mail.thread')
         if message_id and mail_ids :
             mail_record = mail_message.browse(cr, uid, mail_ids)[0]
             res_id = mail_record.res_id