diff --git a/.gitignore b/.gitignore
index 589d00dc..d803a873 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,4 @@ Gemfile.lock
 .project
 .buildpath
 *~ 
+.tool-versions
diff --git a/Gemfile b/Gemfile
index c98072f2..29ee730a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -15,3 +15,4 @@ gem "wikicloth", "=0.8.3"
 gem "twitter-text", "~> 1.14"
 gem "asciidoctor", "~> 2.0.5"
 gem "rake"
+gem "rexml", "~> 3.2", ">= 3.2.5"
diff --git a/github-markup.gemspec b/github-markup.gemspec
index 594d3507..d854a6f1 100644
--- a/github-markup.gemspec
+++ b/github-markup.gemspec
@@ -24,7 +24,8 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'minitest', '~> 5.4', '>= 5.4.3'
   s.add_development_dependency 'html-pipeline', '~> 1.0'
   s.add_development_dependency 'sanitize', '>= 4.6.3'
-  s.add_development_dependency 'nokogiri', '~> 1.8.1'
+  s.add_development_dependency 'nokogiri', '~> 1.16.0'
   s.add_development_dependency 'nokogiri-diff', '~> 0.2.0'
-  s.add_development_dependency "github-linguist", ">= 7.1.3"
+  s.add_development_dependency "github-linguist", ">= 7.2.8"
+  s.add_development_dependency "yajl-ruby", "~> 1.4.1"
 end