diff --git a/ngmin-rails.gemspec b/ngmin-rails.gemspec
index ccd084d..2ce3d75 100644
--- a/ngmin-rails.gemspec
+++ b/ngmin-rails.gemspec
@@ -19,6 +19,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.add_dependency "rails", ">= 3.1"
+  spec.add_dependency "execjs"
   spec.add_development_dependency "bundler", "~> 1.3"
   spec.add_development_dependency "rake"
 end