diff --git a/site-cookbooks/kosmos-mastodon/recipes/default.rb b/site-cookbooks/kosmos-mastodon/recipes/default.rb
index 58df06f..28c48f8 100644
--- a/site-cookbooks/kosmos-mastodon/recipes/default.rb
+++ b/site-cookbooks/kosmos-mastodon/recipes/default.rb
@@ -101,6 +101,10 @@ application mastodon_path do
     version ruby_version
   end
 
+  ruby_gem 'bundler' do
+    version "1.17.3" # 2.0 needs Ruby 2.6 or RubyGems 3.0
+  end
+
   git do
     user "mastodon"
     group "mastodon"