diff --git a/addons/sale_purchase/models/sale_order.py b/addons/sale_purchase/models/sale_order.py
index 8960907f9ed..0b85753411f 100644
--- a/addons/sale_purchase/models/sale_order.py
+++ b/addons/sale_purchase/models/sale_order.py
@@ -114,8 +114,8 @@ class SaleOrderLine(models.Model):
         decreased_values = {}
         if 'product_uom_qty' in values:
             precision = self.env['decimal.precision'].precision_get('Product Unit of Measure')
-            increased_lines = self.sudo().filtered(lambda r: r.purchase_line_count and float_compare(r.product_uom_qty, values['product_uom_qty'], precision_digits=precision) == -1)
-            decreased_lines = self.sudo().filtered(lambda r: r.purchase_line_count and float_compare(r.product_uom_qty, values['product_uom_qty'], precision_digits=precision) == 1)
+            increased_lines = self.sudo().filtered(lambda r: r.product_id.service_to_purchase and r.purchase_line_count and float_compare(r.product_uom_qty, values['product_uom_qty'], precision_digits=precision) == -1)
+            decreased_lines = self.sudo().filtered(lambda r: r.product_id.service_to_purchase and r.purchase_line_count and float_compare(r.product_uom_qty, values['product_uom_qty'], precision_digits=precision) == 1)
             increased_values = {line.id: line.product_uom_qty for line in increased_lines}
             decreased_values = {line.id: line.product_uom_qty for line in decreased_lines}
 
diff --git a/addons/stock_dropshipping/tests/test_dropship.py b/addons/stock_dropshipping/tests/test_dropship.py
index f70897f9eb8..9048fb2d009 100644
--- a/addons/stock_dropshipping/tests/test_dropship.py
+++ b/addons/stock_dropshipping/tests/test_dropship.py
@@ -45,7 +45,7 @@ class TestDropship(common.TransactionCase):
         self.assertAlmostEqual(po_line.product_qty, 1.00)
 
         # Update qty on SO and check PO
-        so.order_line.product_uom_qty = 2.00
+        so.write({'order_line': [[1, so.order_line.id, {'product_uom_qty': 2.00}]]})
         self.assertAlmostEqual(po_line.product_qty, 2.00)
 
         # Create a new so line