Parameter guide of app_indicator_set_label does nothing

When dynamically setting a label with app_indicator_set_label(), the width of an indicator changes. As per the docs at http://developer.ubuntu.com/api/devel/ubuntu-12.04/c/AppIndicator3-0.1.html, the parameter guide can be specified to give a maximum size. Whatever string is given in guide however, the behaviour does not change and the whole bar of indicators does jiggle as before

The docs say:

gchar*"label-guide"read/write

An optional string to provide guidance to the panel on how big the #AppIndicator:label string could get. If this is set correctly then the panel should never 'jiggle' as the string adjusts through out the range of options. For instance, if you were providing a percentage like "54% thrust" in #AppIndicator:label you'd want to set this string to "100% thrust" to ensure space when Scotty can get you enough power.