diff --git a/lib/exception_notifier/email_notifier.rb b/lib/exception_notifier/email_notifier.rb
index cf9fdec1..af1759cc 100644
--- a/lib/exception_notifier/email_notifier.rb
+++ b/lib/exception_notifier/email_notifier.rb
@@ -1,3 +1,4 @@
+require "active_support/core_ext/hash/reverse_merge"
 require 'action_mailer'
 require 'action_dispatch'
 require 'pp'