diff --git a/omniauth-rails_csrf_protection.gemspec b/omniauth-rails_csrf_protection.gemspec
index bc689fe..4f65266 100644
--- a/omniauth-rails_csrf_protection.gemspec
+++ b/omniauth-rails_csrf_protection.gemspec
@@ -22,8 +22,8 @@ Gem::Specification.new do |spec|
   spec.homepage    = "https://github.com/cookpad/omniauth-rails_csrf_protection"
   spec.license     = "MIT"
 
-  spec.files       = Dir['lib/**/*.rb', 'LICENSE.txt', 'README.md']
-  spec.test_files  = Dir['test/**/*.rb']
+  spec.files       = Dir["lib/**/*.rb", "LICENSE.txt", "README.md"]
+  spec.test_files  = Dir["test/**/*.rb"]
 
   spec.require_paths = ["lib"]