diff --git a/ChangeLog b/ChangeLog
index a9a7c2f6f8..4da00ef7fc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Apr  8 07:16:19 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/irb/cmd/help.rb (IRB::ExtendCommand::Help#execute): use RI
+	  interactive mode if no argument.  [ruby-dev:39839]
+
 Wed Apr  8 02:33:55 2010  Marc-Andre Lafortune  <ruby-core@marc-andre.ca>
 
 	* array.c (rb_ary_permutation): Remove limitation for lengthy permutations
diff --git a/lib/irb/cmd/help.rb b/lib/irb/cmd/help.rb
index d2d6ef4083..b946ec01fc 100644
--- a/lib/irb/cmd/help.rb
+++ b/lib/irb/cmd/help.rb
@@ -9,7 +9,6 @@
 #
 
 require 'rdoc/ri/driver'
-require 'rdoc/ri/util'
 
 require "irb/cmd/nop.rb"
 
@@ -21,6 +20,10 @@ module IRB
       rescue SystemExit
       else
         def execute(*names)
+          if names.empty?
+            Ri.interactive
+            return
+          end
           names.each do |name|
             begin
               Ri.get_info_for(name.to_s)