JXA: Error 6: An error occurred. It works in AppleScript, but not in JXA.

I can't seem to execute Voiceover command with JXA. The following AppleScript works.

tell application "VoiceOver" 
    tell commander to perform command "item chooser" 
end tell 

However, the following script in JXA throws a mystery error.

vo = Application("VoiceOver") 
vo.commander.performCommand("item chooser") 
Error 6: An error occurred. 

I'd really appreciate any help with this! Thanks so much!