diff --git a/erpnext/manufacturing/doctype/work_order/work_order.py b/erpnext/manufacturing/doctype/work_order/work_order.py
index 3397e7940de..3ae24b601cd 100644
--- a/erpnext/manufacturing/doctype/work_order/work_order.py
+++ b/erpnext/manufacturing/doctype/work_order/work_order.py
@@ -1272,11 +1272,15 @@ class WorkOrder(Document):
 				& (ste.purpose == "Material Transfer for Manufacture")
 				& (ste.is_return == 0)
 			)
-			.groupby(ste_child.item_code)
+			.groupby(ste_child.item_code, ste_child.original_item)
 		)
 
 		data = query.run(as_dict=1) or []
-		transferred_items = frappe._dict({d.original_item or d.item_code: d.qty for d in data})
+		# An item's own transfer and its substitutes both key to the original item, so sum them.
+		transferred_items = frappe._dict()
+		for d in data:
+			key = d.original_item or d.item_code
+			transferred_items[key] = flt(transferred_items.get(key)) + flt(d.qty)
 
 		for row in self.required_items:
 			row.db_set(