open a bookmark

I'm using the PdfBookmarkEditor to create bookmarks.  Facades.Bookmark object.   I'm setting the property open = true, because I want the bookmark to be opened by default.   However this does not seem to work.  Is this a known issue?  If not, how can set the bookmark to be expanded when the PDF is opened?

I've also used the Generator.Bookmark in the PDF object.  This has a IsExpanded property which works fine when set to true.