diff --git a/activesupport/lib/active_support/core_ext/class/subclasses.rb b/activesupport/lib/active_support/core_ext/class/subclasses.rb
index 3c4bfc5f1edc5d9832bf8f9311f7c84b1b1e441a..b0f9a8be34363b42c81d50fa5769e3305636f26f 100644
--- a/activesupport/lib/active_support/core_ext/class/subclasses.rb
+++ b/activesupport/lib/active_support/core_ext/class/subclasses.rb
@@ -3,7 +3,8 @@
 
 class Class
   begin
-    ObjectSpace.each_object(Class.new) {}
+    # Test if this Ruby supports each_object against singleton_class
+    ObjectSpace.each_object(Numeric.singleton_class) {}
 
     def descendants # :nodoc:
       descendants = []
@@ -12,7 +13,7 @@ def descendants # :nodoc:
       end
       descendants
     end
-  rescue StandardError # JRuby
+  rescue StandardError # JRuby 9.0.4.0 and earlier
     def descendants # :nodoc:
       descendants = []
       ObjectSpace.each_object(Class) do |k|