diff --git a/addons/mrp/models/mrp_production.py b/addons/mrp/models/mrp_production.py
index 34d64f50fb0..e424be4fd14 100644
--- a/addons/mrp/models/mrp_production.py
+++ b/addons/mrp/models/mrp_production.py
@@ -736,12 +736,18 @@ class MrpProduction(models.Model):
 
     @api.onchange('lot_producing_id')
     def _onchange_lot_producing(self):
-        if self.product_id.tracking == 'serial' and self.lot_producing_id:
-            message, dummy = self.env['stock.quant'].sudo()._check_serial_number(self.product_id,
-                                                                                 self.lot_producing_id,
-                                                                                 self.company_id)
+        res = self._can_produce_serial_number()
+        if res is not True:
+            return res
+
+    def _can_produce_serial_number(self, sn=None):
+        self.ensure_one()
+        sn = sn or self.lot_producing_id
+        if self.product_id.tracking == 'serial' and sn:
+            message, dummy = self.env['stock.quant'].sudo()._check_serial_number(self.product_id, sn, self.company_id)
             if message:
                 return {'warning': {'title': _('Warning'), 'message': message}}
+        return True
 
     @api.onchange('product_id', 'move_raw_ids')
     def _onchange_product_id(self):
diff --git a/addons/mrp/models/mrp_workorder.py b/addons/mrp/models/mrp_workorder.py
index 571de8ea775..a3aabdbf008 100644
--- a/addons/mrp/models/mrp_workorder.py
+++ b/addons/mrp/models/mrp_workorder.py
@@ -437,6 +437,12 @@ class MrpWorkorder(models.Model):
         )
         return interval['hours'] * 60
 
+    @api.onchange('finished_lot_id')
+    def _onchange_finished_lot_id(self):
+        res = self.production_id._can_produce_serial_number(sn=self.finished_lot_id)
+        if res is not True:
+            return res
+
     def write(self, values):
         if 'production_id' in values and any(values['production_id'] != w.production_id.id for w in self):
             raise UserError(_('You cannot link this work order to another manufacturing order.'))
@@ -843,18 +849,6 @@ class MrpWorkorder(models.Model):
                 float_round(self.qty_producing, precision_rounding=rounding)
             )
 
-    def _check_sn_uniqueness(self):
-        """ Alert the user if the serial number as already been produced """
-        if self.product_tracking == 'serial' and self.finished_lot_id:
-            sml = self.env['stock.move.line'].search_count([
-                ('lot_id', '=', self.finished_lot_id.id),
-                ('location_id.usage', '=', 'production'),
-                ('qty_done', '=', 1),
-                ('state', '=', 'done')
-            ])
-            if sml:
-                raise UserError(_('This serial number for product %s has already been produced', self.product_id.name))
-
     def _should_start_timer(self):
         return True