diff --git a/ChangeLog b/ChangeLog
index 8f6f506a3e..99ed9d3c4a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Apr 25 11:02:11 2011  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* ext/ripper/lib/ripper/sexp.rb: fix rdoc arround sexp.
+	  patched by Sho Hashimoto. fixes #4599
+
 Mon Apr 25 08:24:04 2011  Shota Fukumori  <sorah@tubusu.net>
 
 	* random.c (rb_f_rand, random_s_rand): RDocs for them.
diff --git a/ext/ripper/lib/ripper/sexp.rb b/ext/ripper/lib/ripper/sexp.rb
index f2260fe8dd..37040e4c11 100644
--- a/ext/ripper/lib/ripper/sexp.rb
+++ b/ext/ripper/lib/ripper/sexp.rb
@@ -14,13 +14,32 @@ class Ripper
 
   # [EXPERIMENTAL]
   # Parses +src+ and create S-exp tree.
+  # Returns more readable tree rather than Ripper.sexp_raw.
   # This method is for mainly developper use.
   #
   #   require 'ripper'
-  #   require 'pp
+  #   require 'pp'
   #
   #   pp Ripper.sexp("def m(a) nil end")
   #     #=> [:program,
+  #          [[:def,
+  #           [:@ident, "m", [1, 4]],
+  #           [:paren, [:params, [[:@ident, "a", [1, 6]]], nil, nil, nil, nil]],
+  #           [:bodystmt, [[:var_ref, [:@kw, "nil", [1, 9]]]], nil, nil, nil]]]]
+  #
+  def Ripper.sexp(src, filename = '-', lineno = 1)
+    SexpBuilderPP.new(src, filename, lineno).parse
+  end
+
+  # [EXPERIMENTAL]
+  # Parses +src+ and create S-exp tree.
+  # This method is for mainly developper use.
+  #
+  #   require 'ripper'
+  #   require 'pp'
+  #
+  #   pp Ripper.sexp_raw("def m(a) nil end")
+  #     #=> [:program,
   #          [:stmts_add,
   #           [:stmts_new],
   #           [:def,
@@ -32,10 +51,6 @@ class Ripper
   #             nil,
   #             nil]]]]
   #
-  def Ripper.sexp(src, filename = '-', lineno = 1)
-    SexpBuilderPP.new(src, filename, lineno).parse
-  end
-
   def Ripper.sexp_raw(src, filename = '-', lineno = 1)
     SexpBuilder.new(src, filename, lineno).parse
   end