diff --git a/modules/purchase_trade/valuation.py b/modules/purchase_trade/valuation.py
index 23304cd..21d7a57 100644
--- a/modules/purchase_trade/valuation.py
+++ b/modules/purchase_trade/valuation.py
@@ -284,6 +284,10 @@ class ValuationBase(ModelSQL):
                 seen.add(line_id)
         return purchase_lines
 
+    @classmethod
+    def _sale_line_is_unmatched(cls, sale_line):
+        return not cls._matched_purchase_lines_from_sale_line(sale_line)
+
     @classmethod
     def _delete_existing_sale_line(cls, sale_line, selected_types=None):
         Date = Pool().get('ir.date')