diff --git a/beautiful-jekyll-theme.gemspec b/beautiful-jekyll-theme.gemspec
index 4fd5843..27a5e70 100644
--- a/beautiful-jekyll-theme.gemspec
+++ b/beautiful-jekyll-theme.gemspec
@@ -25,4 +25,5 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "bundler", ">= 1.16"
   spec.add_development_dependency "rake", "~> 12.0"
+  spec.add_development_dependency "webrick", "~> 1.8"
 end