diff --git a/ChangeLog b/ChangeLog
index 954672d0f80c02..43838901dec82f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Jan  1 12:23:10 2012  Akinori MUSHA  <knu@iDaemons.org>
+
+	* lib/shellwords.rb (Shellwords#shellescape): Drop the //n flag
+	  that only causes warnings with no real effect.  [Bug #5637]
+
 Sat Dec 31 06:28:37 2011  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* thread.c (rb_barrier_waiting): save the number of waiting threads
diff --git a/lib/shellwords.rb b/lib/shellwords.rb
index 5d6ba7544eb535..a83d1f1c86c513 100644
--- a/lib/shellwords.rb
+++ b/lib/shellwords.rb
@@ -75,15 +75,21 @@ class << self
   #     # ...
   #   }
   #
+  # It is caller's responsibility to encode the string in the right
+  # encoding for the shell environment where this string is used.
+  # Multibyte characters are treated as multibyte characters, not
+  # bytes.
+  #
   def shellescape(str)
     # An empty argument will be skipped, so return empty quotes.
     return "''" if str.empty?
 
     str = str.dup
 
-    # Process as a single byte sequence because not all shell
-    # implementations are multibyte aware.
-    str.gsub!(/([^A-Za-z0-9_\-.,:\/@\n])/n, "\\\\\\1")
+    # Treat multibyte characters as is.  It is caller's responsibility
+    # to encode the string in the right encoding for the shell
+    # environment.
+    str.gsub!(/([^A-Za-z0-9_\-.,:\/@\n])/, "\\\\\\1")
 
     # A LF cannot be escaped with a backslash because a backslash + LF
     # combo is regarded as line continuation and simply ignored.
diff --git a/test/test_shellwords.rb b/test/test_shellwords.rb
index d48a8882c8ab06..593f0e0aeadfe8 100644
--- a/test/test_shellwords.rb
+++ b/test/test_shellwords.rb
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 require 'test/unit'
 require 'shellwords'
 
@@ -36,4 +37,11 @@ def test_unmatched_quotes
       shellwords(bad_cmd)
     end
   end
+
+  def test_multibyte_characters
+    # This is not a spec.  It describes the current behavior which may
+    # be changed in future.  There would be no multibyte character
+    # used as shell meta-character that needs to be escaped.
+    assert_equal "\\あ\\い", "あい".shellescape
+  end
 end