diff --git a/liquidation.py b/liquidation.py
index ed6a0d6..dcf8f74 100644
--- a/liquidation.py
+++ b/liquidation.py
@@ -1091,6 +1091,7 @@ class LiquidationExportReport(Report):
                 parties[employee_id]['employee_position'] = position_contract or position_employee or ''
 
             for line in liquidation.lines:
+                concept = None
                 if line.wage.type_concept in (payments):
                     concept = line.wage.type_concept
                 else: