diff --git a/addons/product_expiry/models/production_lot.py b/addons/product_expiry/models/production_lot.py
index 4da3dc74d08..0b8f32c03fd 100644
--- a/addons/product_expiry/models/production_lot.py
+++ b/addons/product_expiry/models/production_lot.py
@@ -47,8 +47,9 @@ class StockLot(models.Model):
                 lot.alert_date = False
             elif lot.expiration_date:
                 # when create
-                if lot.product_id != lot._origin.product_id or\
-                   (not lot.use_date and not lot.removal_date and not lot.alert_date):
+                if lot.product_id != lot._origin.product_id or \
+                   (not lot.use_date and not lot.removal_date and not lot.alert_date) or \
+                   (lot.expiration_date and not lot._origin.expiration_date):
                     product_tmpl = lot.product_id.product_tmpl_id
                     lot.use_date = lot.expiration_date - datetime.timedelta(days=product_tmpl.use_time)
                     lot.removal_date = lot.expiration_date - datetime.timedelta(days=product_tmpl.removal_time)
@@ -56,9 +57,9 @@ class StockLot(models.Model):
                 # when change
                 elif lot._origin.expiration_date:
                     time_delta = lot.expiration_date - lot._origin.expiration_date
-                    lot.use_date = lot.use_date and lot.use_date + time_delta
-                    lot.removal_date = lot.removal_date and lot.removal_date + time_delta
-                    lot.alert_date = lot.alert_date and lot.alert_date + time_delta
+                    lot.use_date = lot._origin.use_date and lot._origin.use_date + time_delta
+                    lot.removal_date = lot._origin.removal_date and lot._origin.removal_date + time_delta
+                    lot.alert_date = lot._origin.alert_date and lot._origin.alert_date + time_delta
 
     @api.model
     def _alert_date_exceeded(self):
diff --git a/addons/product_expiry/tests/test_stock_lot.py b/addons/product_expiry/tests/test_stock_lot.py
index f3af6d487f2..3ee0f1619f9 100644
--- a/addons/product_expiry/tests/test_stock_lot.py
+++ b/addons/product_expiry/tests/test_stock_lot.py
@@ -236,6 +236,20 @@ class TestStockLot(TestStockCommon):
     def test_03_onchange_expiration_date(self):
         """ Updates the `expiration_date` of the lot production and checks other date
         fields are updated as well. """
+        def check_expiration_dates(product, lot, start_date, delta):
+            self.assertAlmostEqual(
+                start_date + timedelta(days=product.expiration_time),
+                lot.expiration_date, delta=delta)
+            self.assertAlmostEqual(
+                lot.expiration_date - timedelta(days=product.use_time),
+                lot.use_date, delta=delta)
+            self.assertAlmostEqual(
+                lot.expiration_date - timedelta(days=product.removal_time),
+                lot.removal_date, delta=delta)
+            self.assertAlmostEqual(
+                lot.expiration_date - timedelta(days=product.alert_time),
+                lot.alert_date, delta=delta)
+
         # Keeps track of the current datetime and set a delta for the compares.
         today_date = datetime.today()
         time_gap = timedelta(seconds=10)
@@ -246,37 +260,36 @@ class TestStockLot(TestStockCommon):
         lot_form.company_id = self.env.company
         apple_lot = lot_form.save()
         # ...then checks date fields have the expected values.
-        self.assertAlmostEqual(
-            today_date + timedelta(days=self.apple_product.expiration_time),
-            apple_lot.expiration_date, delta=time_gap)
-        self.assertAlmostEqual(
-            apple_lot.expiration_date - timedelta(days=self.apple_product.use_time),
-            apple_lot.use_date, delta=time_gap)
-        self.assertAlmostEqual(
-            apple_lot.expiration_date - timedelta(days=self.apple_product.removal_time),
-            apple_lot.removal_date, delta=time_gap)
-        self.assertAlmostEqual(
-            apple_lot.expiration_date - timedelta(days=self.apple_product.alert_time),
-            apple_lot.alert_date, delta=time_gap)
+        check_expiration_dates(self.apple_product, apple_lot, today_date, time_gap)
 
         difference = timedelta(days=20)
-        new_date = apple_lot.expiration_date + difference
-        old_use_date = apple_lot.use_date
-        old_removal_date = apple_lot.removal_date
-        old_alert_date = apple_lot.alert_date
+        new_expiration_date = apple_lot.expiration_date + difference
+        new_start_date = new_expiration_date - timedelta(days=self.apple_product.expiration_time)
+        random_date = new_expiration_date + difference
 
-        # Modifies the lot `expiration_date`...
+        # Modifies the lot `expiration_date` several times, without saving...
         lot_form = Form(apple_lot)
-        lot_form.expiration_date = new_date
+        lot_form.expiration_date = new_expiration_date
+        lot_form.expiration_date = random_date
+        lot_form.expiration_date = new_expiration_date
         apple_lot = lot_form.save()
 
-        # ...then checks all other date fields were correclty updated.
-        self.assertAlmostEqual(
-            apple_lot.use_date, old_use_date + difference, delta=time_gap)
-        self.assertAlmostEqual(
-            apple_lot.removal_date, old_removal_date + difference, delta=time_gap)
-        self.assertAlmostEqual(
-            apple_lot.alert_date, old_alert_date + difference, delta=time_gap)
+        # ...then checks all other date fields were correctly updated.
+        check_expiration_dates(self.apple_product, apple_lot, new_start_date, time_gap)
+
+        # Remove all dates, save, update expiration date twice, then save again
+        lot_form = Form(apple_lot)
+        lot_form.expiration_date = False
+        lot_form.use_date = False
+        lot_form.removal_date = False
+        lot_form.alert_date = False
+        lot_form.save()
+        lot_form.expiration_date = random_date
+        lot_form.expiration_date = new_expiration_date
+        apple_lot = lot_form.save()
+
+        # ...then check all other date fields were correctly updated.
+        check_expiration_dates(self.apple_product, apple_lot, new_start_date, time_gap)
 
     def test_04_expiration_date_on_receipt(self):
         """ Test we can set an expiration date on receipt and all expiration