2 files changed, 7 insertions, 5 deletions
diff --git a/activesupport/lib/active_support/message_encryptor.rb b/activesupport/lib/active_support/message_encryptor.rb
index 27fd061947..5236c776dd 100644
--- a/activesupport/lib/active_support/message_encryptor.rb
+++ b/activesupport/lib/active_support/message_encryptor.rb
@@ -81,9 +81,9 @@ module ActiveSupport
   class MessageEncryptor
     prepend Messages::Rotator::Encryptor
 
-    class << self
-      attr_accessor :use_authenticated_message_encryption #:nodoc:
+    cattr_accessor :use_authenticated_message_encryption, instance_accessor: false, default: false
 
+    class << self
       def default_cipher #:nodoc:
         if use_authenticated_message_encryption
           "aes-256-gcm"
diff --git a/activesupport/lib/active_support/railtie.rb b/activesupport/lib/active_support/railtie.rb
index 91872e29c8..635d98367e 100644
--- a/activesupport/lib/active_support/railtie.rb
+++ b/activesupport/lib/active_support/railtie.rb
@@ -10,9 +10,11 @@ module ActiveSupport
     config.eager_load_namespaces << ActiveSupport
 
     initializer "active_support.set_authenticated_message_encryption" do |app|
-      if app.config.active_support.respond_to?(:use_authenticated_message_encryption)
-        ActiveSupport::MessageEncryptor.use_authenticated_message_encryption =
-          app.config.active_support.use_authenticated_message_encryption
+      config.after_initialize do
+        unless app.config.active_support.use_authenticated_message_encryption.nil?
+          ActiveSupport::MessageEncryptor.use_authenticated_message_encryption =
+            app.config.active_support.use_authenticated_message_encryption
+        end
       end
     end