diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index 13d7c6b7811219f79e7b109726d760c0a67b96cf..2fd2ea896b4b5d65e50e23458ac2686c0929ab78 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -23,7 +23,7 @@ module AttributeMethods
       def self.set_name_cache(name, value)
         const_name = "ATTR_#{name}"
         unless const_defined? const_name
-          const_set const_name, value
+          const_set const_name, value.dup.freeze
         end
       end
     }