Does g_form.onUserChangeValue work with unchecking checkbox?

I have a form that needs to do an AJAX call on any field change. I thought this was a good use case for onUserChangeValue

 var handler = function(fieldname, originalValue, newValue) {
       console.log('The field ('+ fieldname + ') has a new value of: ' + newValue);
 }
 var unregister = g_form.onUserChangeValue(handler);

However, the function is called only when a checkbox is checked, not when it is unchecked. Is this expected behavior? Is there any workaround?