Error $.fn.superfish.o is undefined

After upgrading a client site we started getting a Javascript error...

$.fn.superfish.o is undefined

I tracked down the cause in a thread in the jQuery forums here...

http://forum.jquery.com/topic/jquery-superfish-1-4-8-w-supposition

The following change was made in supposition.js

line 57:
var o = $.superfish.o[this.serial]; /* get this menu's options */
var o = $.fn.superfish.o[this.serial]; /* get this menu's options
*/
line 64:
$.extend($.superfish.o[this.serial],{
$.extend($.fn.superfish.o[this.serial],{

This change was causing the errors in the recently updated Drupal install using...

Drupal 6.28
Superfish 6.x-1.91

and the superfish library linked form the project page

https://github.com/mehrpadin/Superfish-for-Drupal/archive/1.x.zip

After reversing the changes in supposition.js the errors have disappeared. Perhaps the 6.x version of the module needs to use an earlier release of superfish.js?