diff --git a/addons/account/models/account_move.py b/addons/account/models/account_move.py
index efc38f5115a..de72d8e4f36 100644
--- a/addons/account/models/account_move.py
+++ b/addons/account/models/account_move.py
@@ -240,7 +240,7 @@ class AccountMove(models.Model):
 
     # === Hash Fields === #
     restrict_mode_hash_table = fields.Boolean(related='journal_id.restrict_mode_hash_table')
-    secure_sequence_number = fields.Integer(string="Inalteralbility No Gap Sequence #", readonly=True, copy=False)
+    secure_sequence_number = fields.Integer(string="Inalteralbility No Gap Sequence #", readonly=True, copy=False, index=True)
     inalterable_hash = fields.Char(string="Inalterability Hash", readonly=True, copy=False)
     string_to_hash = fields.Char(compute='_compute_string_to_hash', readonly=True)
 
@@ -2631,7 +2631,7 @@ class AccountMove(models.Model):
         """ Returns the hash to write on journal entries when they get posted"""
         self.ensure_one()
         #get the only one exact previous move in the securisation sequence
-        prev_move = self.search([('state', '=', 'posted'),
+        prev_move = self.sudo().search([('state', '=', 'posted'),
                                  ('company_id', '=', self.company_id.id),
                                  ('journal_id', '=', self.journal_id.id),
                                  ('secure_sequence_number', '!=', 0),