diff --git a/src/backend/InvenTree/stock/models.py b/src/backend/InvenTree/stock/models.py
index ee58ba62e0..3a65f2c2f6 100644
--- a/src/backend/InvenTree/stock/models.py
+++ b/src/backend/InvenTree/stock/models.py
@@ -1107,7 +1107,11 @@ class StockItem(
 
         item.add_tracking_entry(code, user, deltas, notes=notes)
 
-        trigger_event('stockitem.assignedtocustomer', id=self.id, customer=customer.id)
+        trigger_event(
+            'stockitem.assignedtocustomer',
+            id=self.id,
+            customer=customer.id if customer else None,
+        )
 
         # Return the reference to the stock item
         return item