Running an action via scripting with options

Hi. Out of interest I'm trying to set some options when running an action via a script, specifically suppressing the action dialog via script. - Not displayDialogs = DialogModes.NO

var theFiles = ["D:\\temp\\jp.jpg"];

// MAIN SCRIPT CODE TO DO STUFF...
var act = "make_layer"
var actset = "my_action_set";

var batchOptions = new BatchOptions();
batchOptions.overrideOpen = false;
batchOptions.overrideSave = false;

// app.doAction(act, actset);
app.batch (theFiles, act, actset, batchOptions)

I get the error illegal argument on app.batch (theFiles, act, actset, batchOptions);  - not very helpful. Not sure where I'm going wrong as 

app.doAction(act, actset);

 works fine.

Any ideas??