diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index 1e5cd25527..30cbba26b0 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -1,4 +1,5 @@
 require 'abstract_unit'
+require 'builder'
 
 class HashExtTest < Test::Unit::TestCase
   def setup