diff --git a/addons/purchase_stock/models/stock.py b/addons/purchase_stock/models/stock.py
index 887afb6b99ca89acd2c3bc3d34e03a67ce52e0bc..7f131ba3da56dd407e2eabca87d5ed7954757fa7 100644
--- a/addons/purchase_stock/models/stock.py
+++ b/addons/purchase_stock/models/stock.py
@@ -19,7 +19,7 @@ class StockMove(models.Model):
     purchase_line_id = fields.Many2one('purchase.order.line',
         'Purchase Order Line', ondelete='set null', index=True, readonly=True)
     created_purchase_line_id = fields.Many2one('purchase.order.line',
-        'Created Purchase Order Line', ondelete='set null', readonly=True, copy=False)
+        'Created Purchase Order Line', ondelete='set null', readonly=True, copy=False, index=True)
 
     @api.model
     def _prepare_merge_moves_distinct_fields(self):