diff --git a/lib/validators/alternative_reply_by_email_addresses_validator.rb b/lib/validators/alternative_reply_by_email_addresses_validator.rb
index 412059ce86e..97b9ddad12f 100644
--- a/lib/validators/alternative_reply_by_email_addresses_validator.rb
+++ b/lib/validators/alternative_reply_by_email_addresses_validator.rb
@@ -1,3 +1,5 @@
+require 'validators/reply_by_email_address_validator'
+
 class AlternativeReplyByEmailAddressesValidator
   def initialize(opts = {})
     @opts = opts