diff --git a/test/test_execjs.rb b/test/test_execjs.rb
index fa162d7..fa4ef02 100644
--- a/test/test_execjs.rb
+++ b/test/test_execjs.rb
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 require "minitest/autorun"
 require "execjs/module"
+require "json"
 
 begin
   require "execjs"