LibXML error when calling #to_xml more than once on a command with extension loaded

[jph]

Full text of error:

LibXML::XML::Error:  Nodes belong to different documents.  You must first import the node by calling XML::Document.import.
from gems/epp-client-2.1.0/lib/epp-client/requests/extension.rb:21:in `<<'

This may be as simple as me not setting namespaces (I've found a few methods called 'set_namespaces') but I'm unable to see exactly how to set these manually.

Below are steps to reproduce.

@domain_update = EPP::Domain::Update.new('example.com',
  :add => {:ns => %w(ns1.test.host ns2.test.host)},
  :rem => {:ns => %w(ns3.test.host ns4.test.host)},
  :chg => {
    :registrant => 'UK-2349723',
    :auth_info => {:pw => '2381728348'}
})

@update = EPP::Commands::Update.new(@domain_update)

explanation = 'explanation'
method = 'update'

# XML GENERATION
      xml = XML::Node.new(method)
      xml.namespaces.namespace = ns = XML::Namespace.new(xml, 'auext', 'urn:X-au:params:xml:ns:auext-1.1')
      xattr = XML::Attr.new(xml, 'schemaLocation', 'urn:X-au:params:xml:ns:auext-1.1 auext-1.1.xsd')
      xattr.namespaces.namespace = XML::Namespace.new(xml, 'xsi', 'http://www.w3.org/2001/XMLSchema-instance')
      au_properties = XML::Node.new('auProperties', '', ns)

      au_properties << node = XML::Node.new('registrantName',  'Registrant Name', ns)
      au_properties << node = XML::Node.new('registrantID',    'Registrant ID', ns)
      node['type'] = 'Registrant ID Type'
      au_properties << node = XML::Node.new('eligibilityName', 'Elig Name', ns)
      au_properties << node = XML::Node.new('eligibilityType', 'Elig Type', ns)
      au_properties << node = XML::Node.new('eligibilityID',  'Elig ID', ns)
      node['type'] = 'Elig Type'
      au_properties << node = XML::Node.new('policyReason', '1', ns)

      xml << au_properties
      xml << XML::Node.new('explanation', explanation, ns) if explanation
# XML GENERATION

@extension = EPP::Requests::Extension.new(xml)

@command = EPP::Requests::Command.new(SecureRandom.uuid, @update, @extension)
@request = EPP::Request.new(@command)

puts @request.to_xml # => this works
puts @request.to_xml # => this throws LibXML::XML::Error