diff --git a/addons/stock/models/stock_picking.py b/addons/stock/models/stock_picking.py
index afac46d705b..ea404b41e5c 100644
--- a/addons/stock/models/stock_picking.py
+++ b/addons/stock/models/stock_picking.py
@@ -591,14 +591,25 @@ class Picking(models.Model):
         self.ensure_one()
         if not self.move_lines and not self.move_line_ids:
             raise UserError(_('Please add some lines to move'))
+
+        # If no lots when needed, raise error
+        picking_type = self.picking_type_id
+        no_quantities_done = all(line.qty_done == 0.0 for line in self.move_line_ids)
+        if picking_type.use_create_lots or picking_type.use_existing_lots:
+            lines_to_check = self.move_line_ids
+            if not no_quantities_done:
+                lines_to_check = lines_to_check.filtered(
+                    lambda line: float_compare(line.qty_done, 0,
+                                               precision_rounding=line.product_uom_id.rounding)
+                )
+
+            for line in lines_to_check:
+                product = line.product_id
+                if product and product.tracking != 'none' and (line.qty_done == 0 or (not line.lot_name and not line.lot_id)):
+                    raise UserError(_('You need to supply a lot/serial number for %s.') % product.name)
+
         # In draft or with no pack operations edited yet, ask if we can just do everything
-        if self.state == 'draft' or all([x.qty_done == 0.0 for x in self.move_line_ids]):
-            # If no lots when needed, raise error
-            picking_type = self.picking_type_id
-            if (picking_type.use_create_lots or picking_type.use_existing_lots):
-                for pack in self.move_line_ids:
-                    if pack.product_id and pack.product_id.tracking != 'none':
-                        raise UserError(_('Some products require lots/serial numbers, so you need to specify those first!'))
+        if self.state == 'draft' or no_quantities_done:
             view = self.env.ref('stock.view_immediate_transfer')
             wiz = self.env['stock.immediate.transfer'].create({'pick_id': self.id})
             return {
diff --git a/addons/stock/tests/test_move.py b/addons/stock/tests/test_move.py
index 2fc3d884045..e935b26c456 100644
--- a/addons/stock/tests/test_move.py
+++ b/addons/stock/tests/test_move.py
@@ -2291,6 +2291,61 @@ class StockMove(TransactionCase):
         self.assertEqual(self.env['stock.quant']._get_available_quantity(self.product1, self.stock_location), 0.0)
         self.assertEqual(len(self.env['stock.quant']._gather(self.product1, self.stock_location)), 0.0)
 
+    def test_immediate_validate_5(self):
+        """ Create a picking and simulates validate button effect.
+            This tests two cases:
+            - if a user has processed no quantities and at least one product is tracked,
+              he should specify lots
+            - if a user has processed some quantities then it's ok because a backorder
+              will be created for the ones not filled in
+        """
+        picking_type = self.env.ref('stock.picking_type_in')
+        picking_type.use_create_lots = True
+        picking_type.use_existing_lots = False
+        lot1 = self.env['stock.production.lot'].create({
+            'name': 'lot1',
+            'product_id': self.product3.id,
+        })
+        self.env['stock.quant']._update_available_quantity(self.product1, self.stock_location, 1)
+        self.env['stock.quant']._update_available_quantity(self.product3, self.stock_location, 1, lot_id=lot1)
+        picking = self.env['stock.picking'].create({
+            'location_id': self.supplier_location.id,
+            'location_dest_id': self.stock_location.id,
+            'picking_type_id': picking_type.id,
+        })
+        self.env['stock.move'].create({
+            'name': 'product1_move',
+            'location_id': self.supplier_location.id,
+            'location_dest_id': self.stock_location.id,
+            'picking_id': picking.id,
+            'product_id': self.product1.id,
+            'product_uom': self.uom_unit.id,
+            'product_uom_qty': 1,
+        })
+        product3_move = self.env['stock.move'].create({
+            'name': 'product3_move',
+            'location_id': self.supplier_location.id,
+            'location_dest_id': self.stock_location.id,
+            'picking_id': picking.id,
+            'product_id': self.product3.id,
+            'product_uom': self.uom_unit.id,
+            'product_uom_qty': 1,
+        })
+        picking.action_confirm()
+        picking.action_assign()
+        with self.assertRaises(UserError):
+            picking.button_validate()
+
+        product3_move.move_line_ids[0].qty_done = 1
+        # should still complain about lots because no lot_{name,id} was set
+        with self.assertRaises(UserError):
+            picking.button_validate()
+
+        product3_move.move_line_ids[0].lot_name = '271828'
+        action = picking.button_validate()  # should open backorder wizard
+        self.assertTrue(isinstance(action, dict), 'Should open backorder wizard')
+        self.assertEqual(action.get('res_model'), 'stock.backorder.confirmation')
+
     def test_set_quantity_done_1(self):
         move1 = self.env['stock.move'].create({
             'name': 'test_set_quantity_done_1',