WPT Script using className on submitForm

Is there a specific limitation on using className for submitForm on chrome to script a login. For example I ran the script at http://www.webpagetest.org/result/130717_V2_1EXT/1/screen_shot/ and see no console errors given this script. What am I doing wrong?

navigate https://www.zoosk.com
setValue name=login_email testuser@aol.com
setValue name=password password
submitForm className=minilogin-form

There shouldn’t be. I opened up a bug to track it: https://github.com/WPO-Foundation/webpagetest/issues/92