Nokogiri under jruby fails to create namespaces named the same as a sibling

dup_namespace.rb

#!/usr/bin/env ruby
 
require 'nokogiri'

d = Nokogiri::XML::Document.new
e1 = d.create_element('e', 'xmlns:foo' => 'fooey')
e2 = d.create_element('e', 'xmlns:foo' => 'fooey')

puts "namespace_definitions should not be empty, but it is"
puts e2.namespace_definitions.inspect