diff --git a/models/res_partner_contract_annex.py b/models/res_partner_contract_annex.py
index f6ac22a..1372853 100644
--- a/models/res_partner_contract_annex.py
+++ b/models/res_partner_contract_annex.py
@@ -98,7 +98,7 @@ class ContractOrderAnnex(models.Model, IDocument, Extension):
 
         # Counter
         record.counter = record.contract_id.contract_annex_number
-        record.contract_id.contract_annex_number += 1
+        record.contract_id.contract_annex_number += 1  # TODO: should I use a sequence?
 
         return record