diff --git a/activesupport/lib/active_support/json/encoding.rb b/activesupport/lib/active_support/json/encoding.rb
index 8ec3af3f504f4..315897b423600 100644
--- a/activesupport/lib/active_support/json/encoding.rb
+++ b/activesupport/lib/active_support/json/encoding.rb
@@ -10,6 +10,7 @@
 require 'active_support/core_ext/hash/slice'
 require 'active_support/core_ext/object/instance_variables'
 require 'time'
+require 'active_support/core_ext/time/conversions'
 
 module ActiveSupport
   class << self