Negative stock allowed for perpetual inventory. Blocked in specific case
diff --git a/erpnext/controllers/buying_controller.py b/erpnext/controllers/buying_controller.py
index 66d5792..cf57658 100644
--- a/erpnext/controllers/buying_controller.py
+++ b/erpnext/controllers/buying_controller.py
@@ -277,6 +277,9 @@
 					"qty": -1 * required_qty,
 					"serial_no": rm.serial_no
 				})
+				if not item_rate:
+					from erpnext.controllers.stock_controller import get_valuation_rate
+					item_rate = get_valuation_rate(bom_item.item_code, self.supplier_warehouse)
 				rm.rate = item_rate or bom_item.rate
 			else:
 				rm.rate = bom_item.rate
diff --git a/erpnext/controllers/stock_controller.py b/erpnext/controllers/stock_controller.py
index ad553d8..a72a3d0 100644
--- a/erpnext/controllers/stock_controller.py
+++ b/erpnext/controllers/stock_controller.py
@@ -30,7 +30,7 @@
 	def get_gl_entries(self, warehouse_account=None, default_expense_account=None,
 			default_cost_center=None, allow_negative_stock=False):
 
-		block_negative_stock(allow_negative_stock)
+		# block_negative_stock(allow_negative_stock)
 
 		if not warehouse_account:
 			warehouse_account = get_warehouse_account()
@@ -319,4 +319,7 @@
 	if not valuation_rate:
 		valuation_rate = frappe.db.get_value("Item Price", {"item_code": item_code, "buying": 1}, "price_list_rate")
 
+	if not valuation_rate:
+		frappe.throw(_("Purchase rate for item: {0} not found, which is required to book accounting entry. Please mention item price against a buying price list.").format(item_code))
+
 	return valuation_rate