diff --git a/Gemfile b/Gemfile
index 17a146f..0529105 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,3 +8,6 @@ gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
 
 # Add wdm to avoid polling on Windows
 gem 'wdm' if Gem.win_platform?
+
+# webrick is not included in Ruby 3.0.0 and later, but it's required for the Jekyll development server.
+gem 'webrick'