Assetupdate from Spark Console returns "incorrect parameters"

Using Spark 4.1.3 on Mac. I just want to update an asset description and leave everything else alone.

assetupdate “1288639315” “My new asset description text” “” “” “” {} “”

returns incorrect parameters. I have tried filling in the old data, and also tried removing the quotes from various parameters. Also tried using the Spark Wallet update itself via the update “pen” icon, which gives another error (json value is not an object as expected). Thoughts?