diff --git a/modules/purchase_trade/service.py b/modules/purchase_trade/service.py
index b723172..52b420b 100644
--- a/modules/purchase_trade/service.py
+++ b/modules/purchase_trade/service.py
@@ -534,10 +534,13 @@ class ContractFactory:
 
     @staticmethod
     def _get_shipment_origin(ct):
-        if ct.shipment_in:
-            return 'stock.shipment.in,%s' % ct.shipment_in.id
-        if ct.shipment_internal:
-            return 'stock.shipment.internal,%s' % ct.shipment_internal.id
-        if ct.shipment_out:
-            return 'stock.shipment.out,%s' % ct.shipment_out.id
+        shipment_in = getattr(ct, 'shipment_in', None)
+        shipment_internal = getattr(ct, 'shipment_internal', None)
+        shipment_out = getattr(ct, 'shipment_out', None)
+        if shipment_in:
+            return 'stock.shipment.in,%s' % shipment_in.id
+        if shipment_internal:
+            return 'stock.shipment.internal,%s' % shipment_internal.id
+        if shipment_out:
+            return 'stock.shipment.out,%s' % shipment_out.id
         return None
diff --git a/modules/purchase_trade/tests/test_module.py b/modules/purchase_trade/tests/test_module.py
index f2d1c50..6eeaaa2 100644
--- a/modules/purchase_trade/tests/test_module.py
+++ b/modules/purchase_trade/tests/test_module.py
@@ -6045,6 +6045,14 @@ class PurchaseTradeTestCase(ModuleTestCase):
         self.assertEqual(line.from_del, '2026-05-01')
         self.assertEqual(line.to_del, '2026-05-31')
 
+    def test_contract_factory_shipment_origin_accepts_partial_context(self):
+        'custom duplicate matched mirror can omit shipment fields'
+        class ContractsStartMock:
+            pass
+
+        self.assertIsNone(
+            ContractFactory._get_shipment_origin(ContractsStartMock()))
+
     def test_lot_matching_rejects_purchase_quantity_above_available(self):
         'apply matching cannot consume more than available purchase quantity'
         class LotQtMock: