class Nokogiri::XML::Document

def root= new_root
  old_root = nil
  if new_root.cstruct[:doc] != cstruct[:doc]
    old_root_ptr = LibXML.xmlDocGetRootElement(cstruct)
    new_root_ptr = LibXML.xmlDocCopyNode(new_root.cstruct, cstruct, 1)
    raise RuntimeError "Could not reparent node (xmlDocCopyNode)" if new_root_ptr.null?
    new_root = Node.wrap(new_root_ptr)
  end
  LibXML.xmlDocSetRootElement(cstruct, new_root.cstruct)
  if old_root_ptr && ! old_root_ptr.null?
    LibXML::XmlNode.new(old_root_ptr).keep_reference_from_document!
  end
  new_root
end