diff --git a/modules/purchase_trade/purchase.py b/modules/purchase_trade/purchase.py
index 3964723..04bef0f 100755
--- a/modules/purchase_trade/purchase.py
+++ b/modules/purchase_trade/purchase.py
@@ -1178,6 +1178,13 @@ class Line(metaclass=PoolMeta):
         values['quantity'] = Decimal(str(quantity)).quantize(
             Decimal("0.00001"))
 
+    @classmethod
+    def _fresh_lines_for_quantity_consistency(cls, lines):
+        try:
+            return [cls(line.id) for line in lines if getattr(line, 'id', None)]
+        except Exception:
+            return lines
+
     @classmethod
     def default_pricing_rule(cls):
         try:
@@ -1680,7 +1687,8 @@ class Line(metaclass=PoolMeta):
                         fee.sync_quantity_from_lots()
                         fee.adjust_purchase_values()
 
-        Pool().get('lot.lot').assert_lines_quantity_consistency(lines)
+        Pool().get('lot.lot').assert_lines_quantity_consistency(
+            cls._fresh_lines_for_quantity_consistency(lines))
 
     @classmethod
     def _sync_open_lot_quantity(cls, line, vlot, target_quantity):
diff --git a/modules/purchase_trade/sale.py b/modules/purchase_trade/sale.py
index 15b44cc..1dcb338 100755
--- a/modules/purchase_trade/sale.py
+++ b/modules/purchase_trade/sale.py
@@ -1137,6 +1137,13 @@ class SaleLine(metaclass=PoolMeta):
         values['quantity'] = Decimal(str(quantity)).quantize(
             Decimal("0.00001"))
 
+    @classmethod
+    def _fresh_lines_for_quantity_consistency(cls, lines):
+        try:
+            return [cls(line.id) for line in lines if getattr(line, 'id', None)]
+        except Exception:
+            return lines
+
     def get_invoice_line(self, lots=None, action=None):
         lines = super().get_invoice_line(lots, action)
         if action != 'prov' or not lots:
@@ -1795,7 +1802,8 @@ class SaleLine(metaclass=PoolMeta):
                 fee.sync_quantity_from_lots()
                 fee.adjust_purchase_values()
 
-        Pool().get('lot.lot').assert_lines_quantity_consistency(lines)
+        Pool().get('lot.lot').assert_lines_quantity_consistency(
+            cls._fresh_lines_for_quantity_consistency(lines))
 
     @classmethod
     def _sync_open_lot_quantity(cls, line, vlot, target_quantity):