Updating Transaction Item Price or Quantity Doesn't Update Gross Value

If an item price or quantity for an existing transaction is changed, the gross amount appearing in the transactions list and the invoice does not reflect the change. If the Total cost is updated in the transaction overview, however, the change is reflected in the gross and invoice values.

Looking at store_transaction_item_save() in store.inc, it updates qty, price and title in the ec_transaction_product table but does not update gross value in the ec_transaction table.