diff --git a/addons/stock/models/product.py b/addons/stock/models/product.py
index fef75714961..632983fab30 100644
--- a/addons/stock/models/product.py
+++ b/addons/stock/models/product.py
@@ -583,3 +583,23 @@ class ProductCategory(models.Model):
             category = category.parent_id
             routes |= category.route_ids
         self.total_route_ids = routes
+
+
+class ProductUoM(models.Model):
+    _inherit = 'product.uom'
+
+    def write(self, values):
+        # Users can not update the factor if open stock moves are based on it
+        if 'factor' in values or 'factor_inv' in values or 'category_id' in values:
+            stock_move_lines = self.env['stock.move.line'].search_count([
+                ('product_uom_id.category_id', '=', self.category_id.id),
+                ('state', '!=', 'cancel'),
+            ])
+
+            if stock_move_lines:
+                raise UserError(_(
+                    "You cannot change the ratio of this unit of mesure as some"
+                    " products with this UoM have already been moved or are "
+                    "currently reserved."
+                ))
+        return super(ProductUoM, self).write(values)
diff --git a/addons/stock/tests/__init__.py b/addons/stock/tests/__init__.py
index a9a18e270e4..f0272143725 100644
--- a/addons/stock/tests/__init__.py
+++ b/addons/stock/tests/__init__.py
@@ -9,3 +9,4 @@ from . import test_quant
 from . import test_inventory
 from . import test_move
 from . import test_move2
+from . import test_robustness
diff --git a/addons/stock/tests/test_robustness.py b/addons/stock/tests/test_robustness.py
new file mode 100644
index 00000000000..4e49a4c9bc1
--- /dev/null
+++ b/addons/stock/tests/test_robustness.py
@@ -0,0 +1,65 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+from odoo.exceptions import UserError
+from odoo.tests.common import TransactionCase
+
+
+class TestRobustness(TransactionCase):
+    def setUp(self):
+        super(TestRobustness, self).setUp()
+        self.stock_location = self.env.ref('stock.stock_location_stock')
+        self.customer_location = self.env.ref('stock.stock_location_customers')
+        self.uom_unit = self.env.ref('product.product_uom_unit')
+        self.uom_dozen = self.env.ref('product.product_uom_dozen')
+        self.product1 = self.env['product.product'].create({
+            'name': 'Product A',
+            'type': 'product',
+            'categ_id': self.env.ref('product.product_category_all').id,
+        })
+
+    def test_uom_factor(self):
+        """ Changing the factor of a unit of measure shouldn't be allowed while
+        quantities are reserved, else the existing move lines won't be consistent
+        with the `reserved_quantity` on quants.
+        """
+        # make some stock
+        self.env['stock.quant']._update_available_quantity(
+            self.product1,
+            self.stock_location,
+            12,
+        )
+
+        # reserve a dozen
+        move1 = self.env['stock.move'].create({
+            'name': 'test_uom_rounding',
+            'location_id': self.stock_location.id,
+            'location_dest_id': self.customer_location.id,
+            'product_id': self.product1.id,
+            'product_uom': self.uom_dozen.id,
+            'product_uom_qty': 1,
+        })
+        move1._action_confirm()
+        move1._action_assign()
+        self.assertEqual(move1.state, 'assigned')
+        quant = self.env['stock.quant']._gather(
+            self.product1,
+            self.stock_location,
+        )
+
+        # assert the reservation
+        self.assertEqual(quant.reserved_quantity, 12)
+        self.assertEqual(move1.product_qty, 12)
+
+        # change the factor
+        with self.assertRaises(UserError):
+            with self.cr.savepoint():
+                move1.product_uom.factor = 0.05
+
+        # assert the reservation
+        self.assertEqual(quant.reserved_quantity, 12)
+        self.assertEqual(move1.state, 'assigned')
+        self.assertEqual(move1.product_qty, 12)
+
+        # unreserve
+        move1._do_unreserve()