diff --git a/addons/sale_stock/models/sale_order.py b/addons/sale_stock/models/sale_order.py
index bcf147c7cd4..3917e2782de 100644
--- a/addons/sale_stock/models/sale_order.py
+++ b/addons/sale_stock/models/sale_order.py
@@ -217,6 +217,13 @@ class SaleOrderLine(models.Model):
         })
         return values
 
+    def _get_qty_procurement(self):
+        self.ensure_one()
+        qty = 0.0
+        for move in self.move_ids.filtered(lambda r: r.state != 'cancel'):
+            qty += move.product_uom._compute_quantity(move.product_uom_qty, self.product_uom, rounding_method='HALF-UP')
+        return qty
+
     @api.multi
     def _action_launch_procurement_rule(self):
         """
@@ -229,9 +236,7 @@ class SaleOrderLine(models.Model):
         for line in self:
             if line.state != 'sale' or not line.product_id.type in ('consu','product'):
                 continue
-            qty = 0.0
-            for move in line.move_ids.filtered(lambda r: r.state != 'cancel'):
-                qty += move.product_uom._compute_quantity(move.product_uom_qty, line.product_uom, rounding_method='HALF-UP')
+            qty = line._get_qty_procurement()
             if float_compare(qty, line.product_uom_qty, precision_digits=precision) >= 0:
                 continue
 
diff --git a/addons/stock_dropshipping/models/__init__.py b/addons/stock_dropshipping/models/__init__.py
index c617a28246d..7d6f1be055f 100644
--- a/addons/stock_dropshipping/models/__init__.py
+++ b/addons/stock_dropshipping/models/__init__.py
@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from . import purchase
\ No newline at end of file
+from . import purchase
+from . import sale
diff --git a/addons/stock_dropshipping/models/sale.py b/addons/stock_dropshipping/models/sale.py
new file mode 100644
index 00000000000..81f975cbce6
--- /dev/null
+++ b/addons/stock_dropshipping/models/sale.py
@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+from odoo import api, models, fields
+
+
+class SaleOrderLine(models.Model):
+    _inherit = "sale.order.line"
+
+    purchase_line_ids = fields.One2many('purchase.order.line', 'sale_line_id')
+
+    @api.multi
+    def _get_qty_procurement(self):
+        if not self.move_ids.filtered(lambda r: r.state != 'cancel') and self.purchase_line_ids.filtered(lambda r: r.state != 'cancel'):
+            qty = 0.0
+            for po_line in self.purchase_line_ids.filtered(lambda r: r.state != 'cancel'):
+                qty += po_line.product_uom._compute_quantity(po_line.product_qty, self.product_uom, rounding_method='HALF-UP')
+            return qty
+        else:
+            return super(SaleOrderLine, self)._get_qty_procurement()
+
diff --git a/addons/stock_dropshipping/tests/__init__.py b/addons/stock_dropshipping/tests/__init__.py
index 4df849a1468..7d0e80dc968 100644
--- a/addons/stock_dropshipping/tests/__init__.py
+++ b/addons/stock_dropshipping/tests/__init__.py
@@ -1,4 +1,4 @@
 # -*- coding: utf-8 -*-
 
+from . import test_dropship
 from . import test_stockvaluation
-
diff --git a/addons/stock_dropshipping/tests/test_dropship.py b/addons/stock_dropshipping/tests/test_dropship.py
new file mode 100644
index 00000000000..7fb7a4ddf7c
--- /dev/null
+++ b/addons/stock_dropshipping/tests/test_dropship.py
@@ -0,0 +1,45 @@
+from odoo.tests.common import TransactionCase
+
+
+class TestDropship(TransactionCase):
+    def test_change_qty(self):
+        # enable the dropship and MTO route on the product
+        prod = self.env.ref('product.product_product_8')
+        dropshipping_route = self.env.ref('stock_dropshipping.route_drop_shipping')
+        mto_route = self.env.ref('stock.route_warehouse0_mto')
+        prod.write({'route_ids': [(6, 0, [dropshipping_route.id, mto_route.id])]})
+
+        # add a vendor
+        vendor1 = self.env['res.partner'].create({'name': 'vendor1'})
+        seller1 = self.env['product.supplierinfo'].create({
+            'name': vendor1.id,
+            'price': 8,
+        })
+        prod.write({'seller_ids': [(6, 0, [seller1.id])]})
+
+        # sell one unit of this product
+        cust = self.env['res.partner'].create({'name': 'customer1'})
+        so = self.env['sale.order'].create({
+            'partner_id': cust.id,
+            'partner_invoice_id': cust.id,
+            'partner_shipping_id': cust.id,
+            'order_line': [(0, 0, {
+                'name': prod.name,
+                'product_id': prod.id,
+                'product_uom_qty': 1.00,
+                'product_uom': prod.uom_id.id,
+                'price_unit': 12,
+            })],
+            'pricelist_id': self.env.ref('product.list0').id,
+            'picking_policy': 'direct',
+        })
+        so.action_confirm()
+        po = self.env['purchase.order'].search([('group_id', '=', so.procurement_group_id.id)])
+        po_line = po.order_line
+
+        # Check the qty on the P0
+        self.assertAlmostEqual(po_line.product_qty, 1.00)
+
+        # Update qty on SO and check PO
+        so.order_line.product_uom_qty = 2.00
+        self.assertAlmostEqual(po_line.product_qty, 2.00)