Hi,

I do have the same problem here with a table 'order_stock_line' inheriting from 'purchase_order_line' like follows : 

class order_stock_line(osv.osv):
    _name = "order.line.stock"
    _inherit = 'purchase.order.line'
    _table = 'order_stock_line'
    _columns = {
        
        'order_stock_id': fields.many2one('purchase.order.stock', 'Order Reference', select=True, ondelete='cascade'),
        'requisition_stock_id': fields.related('order_stock_id','requisition_stock_id',type='many2one',relation='purchase.requisition.stock',string='Requisition sur stock',store=True, select=True, readonly=True),
    }
order_stock_line()

Anytime I want to create a new instance of this object I do have the same message, and I don't know why.

Any comments ? Thanks in advance. ;)