Extended widget selector (:namespace-widgetname) does not work as expected

Well, I'm not sure this is a bug.

I'm not able to check for parent widget instance on the element which running extended widget.

Like this:

$.widget('wdg.testBase', {});
$.widget('wdg.testExtended', $.wdg.testBase, {});

And then:

$('<div>').testExtended().is(':wdg-testBase') -> false, whereas true expected

JSBin sample: http://jsbin.com/loregavufo/edit

Related ticket: http://bugs.jqueryui.com/ticket/4266