breakBefore method not working

I want to insert a page break using scripting but can't get the breakBefore method to work.

Not working:

root.sub2.breakBefore.targetType = "pageArea"
root.sub2.breakBefore.target = "#Page2";

I get the error: "subform does not have property 'breakBefore'."

The deprecated method break.before is working:

root.sub2.break.before = "pageArea";
root.sub2.break.before.target = "Page2"

However, I don't want to use the deprecated break.before method as it causes compability problems with our print supplier, probably because the method is not supported.

Can anyone help?
Documentation: help.adobe.com - breakBefore