diff --git a/Gemfile b/Gemfile
index 493a7b9e..f2fdae87 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,7 +2,7 @@ source 'https://rubygems.org'
 
 require 'json'
 require 'open-uri'
-versions = JSON.parse(open('https://pages.github.com/versions.json').read)
+versions = JSON.parse(URI.open('https://pages.github.com/versions.json').read)
 
 gem 'github-pages', versions['github-pages']
 gem 'pygments.rb'