diff --git a/activesupport/lib/active_support/core_ext/class/attribute.rb b/activesupport/lib/active_support/core_ext/class/attribute.rb
index cd7877fce4..7af3cebc34 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute.rb
@@ -108,8 +108,10 @@ class Class
     end
   end
 
-  private
-  def singleton_class?
-    ancestors.first != self
+private
+  unless respond_to?(:singleton_class?)
+    def singleton_class?
+      ancestors.first != self
+    end
   end
 end