diff --git a/addons/mrp/models/mrp_workorder.py b/addons/mrp/models/mrp_workorder.py
index 23cd851b780..b9e4ea18d74 100644
--- a/addons/mrp/models/mrp_workorder.py
+++ b/addons/mrp/models/mrp_workorder.py
@@ -163,7 +163,7 @@ class MrpWorkorder(models.Model):
                 ('bom_id', '=', workorder.production_id.bom_id.id),
                 ('routing_id', '=', workorder.operation_id.routing_id.id)]
             messages = ProductionMessage.search(domain).mapped('message')
-            workorder.production_messages = "<br/>".join(messages)
+            workorder.production_messages = "<br/>".join(messages) or False
 
     @api.multi
     def _compute_scrap_move_count(self):