diff --git a/lib/pp.rb b/lib/pp.rb
index 0e737d23f6..9acb02f61e 100644
--- a/lib/pp.rb
+++ b/lib/pp.rb
@@ -17,13 +17,14 @@ module Kernel
   # prints arguments in pretty form.
   #
   # pp returns argument(s).
-  undef pp if method_defined?(:pp)
+  alias __pp_backup__ pp if method_defined?(:pp)
   def pp(*objs)
     objs.each {|obj|
       PP.pp(obj)
     }
     objs.size <= 1 ? objs.first : objs
   end
+  undef __pp_backup__ if method_defined?(:__pp_backup__)
   module_function :pp
 end