1 files changed, 3 insertions, 1 deletions
diff --git a/activesupport/lib/active_support/core_ext/class/inheritable_attributes.rb b/activesupport/lib/active_support/core_ext/class/inheritable_attributes.rb
index 2f18666ab9..cca93a0b9f 100644
--- a/activesupport/lib/active_support/core_ext/class/inheritable_attributes.rb
+++ b/activesupport/lib/active_support/core_ext/class/inheritable_attributes.rb
@@ -1,3 +1,5 @@
+require 'active_support/core_ext/object/duplicable'
+
 # Retain for backward compatibility.  Methods are now included in Class.
 module ClassInheritableAttributes # :nodoc:
 end
@@ -216,4 +218,4 @@ class Class
     extlib_inheritable_reader(*syms)
     extlib_inheritable_writer(*syms)
   end
-end
-\ No newline at end of file
+end