diff --git a/l10n_th_account_pit/models/account_voucher.py b/l10n_th_account_pit/models/account_voucher.py
index 0dfd1a354..e7b28310c 100755
--- a/l10n_th_account_pit/models/account_voucher.py
+++ b/l10n_th_account_pit/models/account_voucher.py
@@ -43,6 +43,7 @@ def cancel_voucher(self):
                         'amount_income': -line.amount_income,
                         'amount_wht': -line.amount_wht,
                         'precalc_wht': -line.precalc_wht,
+                        'cancelled': True
                     })
                     # Assign sequence and post
                     pit_line.action_post()