diff --git a/temp_file/Gemfile b/temp_file/Gemfile
index b69807c..04f6f28 100644
--- a/temp_file/Gemfile
+++ b/temp_file/Gemfile
@@ -6,6 +6,11 @@ if $0.to_s.scan('bundle').length==0
     system("bundle install") if !flag
   }
 end
+if RUBY_VERSION.to_f <= 2.1
+  gem 'concurrent-ruby', '~>1.1.9'
+else
+  gem 'concurrent-ruby'
+end
 #built in modules
 eval(File.read(File.dirname(__FILE__) + '/built_in_extensions.rb'))
 #modules installed from the store