diff --git a/accountant/models/accounts.py b/accountant/models/accounts.py
index 272e2ed..17258f8 100644
--- a/accountant/models/accounts.py
+++ b/accountant/models/accounts.py
@@ -102,6 +102,8 @@ class Account(db.Model):
     # pylint: disable=no-self-use
     def validate_authorized_overdraft(self, key, authorized_overdraft):
         """Validator for authorized_overdraft : must be negative."""
+        del key
+
         assert authorized_overdraft <= 0
 
         return authorized_overdraft