Text label for new ribbon groups added to the toolbar

When adding a custom ribbon group to the LiveContent Create toolbar ribbon, the group is displayed with the id as the text. I tried to add a label attribute with different text, but it was ignored. My client would prefer no label:

<x:overlay xmlns="http://xopus.com/2009/lui">

   <!-- Create a new ribbon group -->
   <ribbon-group id="CustomUndoRedoGroup" label="" after="UndoRedoGroup">



Is there any way to accomplish this?