diff --git a/addons/mrp/models/mrp_workorder.py b/addons/mrp/models/mrp_workorder.py
index ab2d159f078..ec8756d543f 100644
--- a/addons/mrp/models/mrp_workorder.py
+++ b/addons/mrp/models/mrp_workorder.py
@@ -297,7 +297,8 @@ class MrpWorkorder(models.Model):
     @api.depends('operation_id', 'workcenter_id', 'qty_production')
     def _compute_duration_expected(self):
         for workorder in self:
-            workorder.duration_expected = workorder._get_duration_expected()
+            if workorder.state not in ['done', 'cancel']:
+                workorder.duration_expected = workorder._get_duration_expected()
 
     @api.depends('time_ids.duration', 'qty_produced')
     def _compute_duration(self):
diff --git a/addons/mrp/tests/test_order.py b/addons/mrp/tests/test_order.py
index d35a2cca166..f1256ae93b9 100644
--- a/addons/mrp/tests/test_order.py
+++ b/addons/mrp/tests/test_order.py
@@ -3798,3 +3798,31 @@ class TestMrpOrder(TestMrpCommon):
         mo_form.product_id = self.product_7_template.product_variant_ids[0]
         mo = mo_form.save()
         self.assertEqual(mo.move_raw_ids.product_id, c3)
+
+    def test_mo_duration_expected(self):
+        """
+        Test to verify that the 'duration_expected' on a work order in a manufacturing order
+        correctly remains as manually set after completion. This test involves creating a product
+        with a Bill of Materials (BOM) and an operation with an initial expected duration.
+        A manufacturing order is then created for this product, the expected duration of the
+        work order is manually changed, and the order is completed. The test checks that
+        the expected duration remains as manually set and does not revert to the original value.
+        """
+        production_form = Form(self.env['mrp.production'])
+        production_form.product_id = self.product_5
+        production_form.bom_id = self.bom_2
+        production_form.product_qty = 1.0
+        production = production_form.save()
+        production.action_confirm()
+
+        init_duration_expected = production.workorder_ids.duration_expected
+
+        production.workorder_ids.duration_expected = init_duration_expected + 5
+
+        production_form = Form(production)
+        production_form.qty_producing = 1.0
+        production = production_form.save()
+
+        production.button_mark_done()
+
+        self.assertEqual(production.workorder_ids.duration_expected, init_duration_expected + 5)