diff --git a/activesupport/lib/active_support/i18n.rb b/activesupport/lib/active_support/i18n.rb
index 188653bd9b..8d8bf02927 100644
--- a/activesupport/lib/active_support/i18n.rb
+++ b/activesupport/lib/active_support/i18n.rb
@@ -1,4 +1,5 @@
 begin
+  require 'active_support/core_ext/hash/deep_merge'
   require 'i18n'
   require 'active_support/lazy_load_hooks'
 rescue LoadError => e