diff --git a/addons/account/models/account_move.py b/addons/account/models/account_move.py
index d8818f1d6e8..d28bc36c2f5 100644
--- a/addons/account/models/account_move.py
+++ b/addons/account/models/account_move.py
@@ -1737,7 +1737,7 @@ class AccountMove(models.Model):
 
     @api.onchange('partner_id')
     def _onchange_partner_id(self):
-        self = self.with_company(self.journal_id.company_id)
+        self = self.with_company(self.journal_id.company_id._accessible_branches()[:1])
 
         warning = {}
         if self.partner_id:
diff --git a/addons/account/models/company.py b/addons/account/models/company.py
index 961d05e9185..26c6d9d1951 100644
--- a/addons/account/models/company.py
+++ b/addons/account/models/company.py
@@ -356,7 +356,8 @@ class ResCompany(models.Model):
         if self.user_has_groups('account.group_account_manager'):
             lock_date = self.fiscalyear_lock_date or date.min
         if self.parent_id:
-            lock_date = max(lock_date, self.parent_id._get_user_fiscal_lock_date())
+            # We need to use sudo, since we might not have access to a parent company.
+            lock_date = max(lock_date, self.sudo().parent_id._get_user_fiscal_lock_date())
         return lock_date
 
     def _get_violated_lock_dates(self, accounting_date, has_tax):