diff --git a/addons/stock/models/stock_rule.py b/addons/stock/models/stock_rule.py
index 71c0063f9c2..1ab9f7d1876 100644
--- a/addons/stock/models/stock_rule.py
+++ b/addons/stock/models/stock_rule.py
@@ -57,7 +57,7 @@ class StockRule(models.Model):
     picking_type_id = fields.Many2one(
         'stock.picking.type', 'Operation Type',
         required=True, check_company=True,
-        domain=[('code', '?=', 'picking_type_code_domain')])
+        domain="[('code', '=?', picking_type_code_domain)]")
     picking_type_code_domain = fields.Char(compute='_compute_picking_type_code_domain')
     delay = fields.Integer('Delay', default=0, help="The expected date of the created transfer will be computed based on this delay.")
     partner_address_id = fields.Many2one(