diff --git a/addons/account/models/account_partial_reconcile.py b/addons/account/models/account_partial_reconcile.py
index f9dad7ab28a..3e3cc8478fc 100644
--- a/addons/account/models/account_partial_reconcile.py
+++ b/addons/account/models/account_partial_reconcile.py
@@ -18,7 +18,7 @@ class AccountPartialReconcile(models.Model):
         index=True, required=True)
     full_reconcile_id = fields.Many2one(
         comodel_name='account.full.reconcile',
-        string="Full Reconcile", copy=False)
+        string="Full Reconcile", copy=False, index='btree_not_null')
     exchange_move_id = fields.Many2one(comodel_name='account.move', index='btree_not_null')
 
     # ==== Currency fields ====