diff --git a/activesupport/lib/active_support/json/encoding.rb b/activesupport/lib/active_support/json/encoding.rb
index 389df58ec485247cd0ff13fa590fefd8299cf4b2..1a95bd63e6334e543e9a416f18574523f3c41f29 100644
--- a/activesupport/lib/active_support/json/encoding.rb
+++ b/activesupport/lib/active_support/json/encoding.rb
@@ -1,5 +1,6 @@
 require 'active_support/core_ext/object/to_json'
 require 'active_support/core_ext/module/delegation'
+require 'active_support/json/variable'
 
 require 'bigdecimal'
 require 'active_support/core_ext/big_decimal/conversions' # for #to_s