diff --git a/lib/devise.rb b/lib/devise.rb
index 429eec6d..9fc667a6 100644
--- a/lib/devise.rb
+++ b/lib/devise.rb
@@ -243,7 +243,9 @@ module Devise
 
   # Set the mailer reference object to access the mailer.
   def self.mailer=(class_name)
-    @@mailer_ref = ActiveSupport::Dependencies.reference(class_name)
+    @@mailer_ref = ActiveSupport::Dependencies.respond_to?(:reference)
+                    ? ActiveSupport::Dependencies.reference(class_name)
+                    : ActiveSupport::Dependencies.ref(class_name)
   end
   self.mailer = "Devise::Mailer"