::BasicObject always defined in ruby 19

activesupport/lib/active_support/basic_object.rb

 module ActiveSupport
-  if defined? ::BasicObject
-    # A class with no predefined methods that behaves similarly to Builder's
-    # BlankSlate. Used for proxy classes.
-    class BasicObject < ::BasicObject
-      undef_method :==
-      undef_method :equal?
+  # A class with no predefined methods that behaves similarly to Builder's
+  # BlankSlate. Used for proxy classes.
+  class BasicObject < ::BasicObject
+    undef_method :==
+    undef_method :equal?
 
-      # Let ActiveSupport::BasicObject at least raise exceptions.
-      def raise(*args)
-        ::Object.send(:raise, *args)
-      end
-    end
-  else
-    class BasicObject #:nodoc:
-      instance_methods.each do |m|
-        undef_method(m) if m.to_s !~ /(?:^__|^nil\?$|^send$|^object_id$)/
-      end
+    # Let ActiveSupport::BasicObject at least raise exceptions.
+    def raise(*args)
+      ::Object.send(:raise, *args)
     end
   end
+
 end