diff --git a/Gemfile b/Gemfile
index f1bd0d9..c1076cf 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,3 +2,6 @@ source 'https://rubygems.org'
 
 gem "jekyll", "~> 3.10"
 gem 'jekyll-tabs'
+gem 'public_suffix', '~> 6.0'
+gem 'concurrent-ruby', '~> 1.3'
+gem 'rexml', '~> 3.3'
diff --git a/Gemfile.lock b/Gemfile.lock
index 800e572..c76f261 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -99,8 +99,11 @@ PLATFORMS
   x86_64-linux-musl
 
 DEPENDENCIES
+  concurrent-ruby (~> 1.3)
   jekyll (~> 3.10)
   jekyll-tabs
+  public_suffix (~> 6.0)
+  rexml (~> 3.3)
 
 BUNDLED WITH
    2.5.17