diff --git a/addons/purchase/models/purchase.py b/addons/purchase/models/purchase.py
index 77d85dda035..81fe7ef0045 100644
--- a/addons/purchase/models/purchase.py
+++ b/addons/purchase/models/purchase.py
@@ -1179,7 +1179,9 @@ class PurchaseOrderLine(models.Model):
         if not self.product_id:
             return
 
-        self.product_uom = self.product_id.uom_po_id or self.product_id.uom_id
+        # TODO: Remove when onchanges are replaced with computes
+        if not (self.env.context.get('origin_po_id') and self.product_uom and self.product_id.uom_id.category_id == self.product_uom_category_id):
+            self.product_uom = self.product_id.uom_po_id or self.product_id.uom_id
         product_lang = self.product_id.with_context(
             lang=get_lang(self.env, self.partner_id.lang).code,
             partner_id=self.partner_id.id,
diff --git a/addons/purchase_requisition/tests/test_purchase_requisition.py b/addons/purchase_requisition/tests/test_purchase_requisition.py
index 4555f36d55d..6c8f8ff76a3 100644
--- a/addons/purchase_requisition/tests/test_purchase_requisition.py
+++ b/addons/purchase_requisition/tests/test_purchase_requisition.py
@@ -285,6 +285,32 @@ class TestPurchaseRequisition(TestPurchaseRequisitionCommon):
             po_1.order_line.price_unit, 16,
             "Line's unit price from the original PO shouldn't be changed")
 
+    def test_10_alternative_po_line_price_unit_different_uom(self):
+        """ Check that the uom is copied in the alternative PO, and the "unit_price"
+        is calculated according to this uom and not that of the product """
+        # Creates a first Purchase Order.
+        po_form = Form(self.env['purchase.order'])
+        self.product_09.standard_price = 10
+        po_form.partner_id = self.res_partner_1
+        with po_form.order_line.new() as line:
+            line.product_id = self.product_09
+            line.product_qty = 1
+            line.product_uom = self.env.ref('uom.product_uom_dozen')
+        po_1 = po_form.save()
+        self.assertEqual(po_1.order_line[0].price_unit, 120)
+
+        # Creates an alternative PO.
+        action = po_1.action_create_alternative()
+        alt_po_wizard_form = Form(self.env['purchase.requisition.create.alternative'].with_context(**action['context']))
+        alt_po_wizard_form.partner_id = self.res_partner_1
+        alt_po_wizard_form.copy_products = True
+        alt_po_wizard = alt_po_wizard_form.save()
+        alt_po_wizard.action_create_alternative()
+
+        po_2 = po_1.alternative_po_ids - po_1
+        self.assertEqual(po_2.order_line[0].product_uom, po_1.order_line[0].product_uom)
+        self.assertEqual(po_2.order_line[0].price_unit, 120)
+
     def test_11_alternative_po_from_po_with_requisition_id(self):
         """Create a purchase order from a blanket order, then check that the alternative purchase order
             can be created and that the requisition_id is not set on it.