I have added a many2one field for incoterm to the delivery order, however I want to pull the value from the sales order if it is set when the delivery order is created.

I tried using a default value calculated by pulling from sale_id.incoterm However this field is not populated at time of stock.picking creation, so it comes up blank. 

I thought about using an onchange, however, onchanges are not called when a recorded is created by the server, so it only works if sale_id is manually changed. 

Is there a better way to set data on a record from another record during creation?