diff --git a/activesupport/lib/active_support/per_thread_registry.rb b/activesupport/lib/active_support/per_thread_registry.rb
index a5e7389d16a78221c1bdca04b9a922d63d0866ac..ca2e4d5625ef94a82873c1a1b98f6faec34a1af1 100644
--- a/activesupport/lib/active_support/per_thread_registry.rb
+++ b/activesupport/lib/active_support/per_thread_registry.rb
@@ -32,12 +32,15 @@ module ActiveSupport
   #
   # If the class has an initializer, it must accept no arguments.
   module PerThreadRegistry
+    def self.extended(object)
+      object.instance_variable_set '@per_thread_registry_key', object.name.freeze
+    end
+
     def instance
-      Thread.current[name] ||= new
+      Thread.current[@per_thread_registry_key] ||= new
     end
 
     protected
-
       def method_missing(name, *args, &block) # :nodoc:
         # Caches the method definition as a singleton method of the receiver.
         define_singleton_method(name) do |*a, &b|