How to edit docx with nokogiri and rubyzip

Question

I'm using a combination of rubyzip and nokogiri to edit a .docx file. I'm using rubyzip to unzip the .docx file and then using nokogiri to parse and change the body of the word/document.xml file but ever time I close rubyzip at the end it corrupts the file and I can't open it or repair it. I unzip the .docx file on desktop and check the word/document.xml file and the content is updated to what I changed it to but all the other files are messed up. Could someone help me with this issue? Here is my code:

require 'rubygems'
require 'zip/zip'
require 'nokogiri'
zip = Zip::ZipFile.open("test.docx")
doc = zip.find_entry("word/document.xml")
xml = Nokogiri::XML.parse(doc.get_input_stream)
wt = xml.root.xpath("//w:t", {"w" => "http://schemas.openxmlformats.org/wordprocessingml/2006/main"}).first
wt.content = "New Text"
zip.get_output_stream("word/document.xml") {|f| f << xml.to_s}
zip.close