diff --git a/lib/webrick/httpservlet/filehandler.rb b/lib/webrick/httpservlet/filehandler.rb
index 601882e..69adad2 100644
--- a/lib/webrick/httpservlet/filehandler.rb
+++ b/lib/webrick/httpservlet/filehandler.rb
@@ -324,7 +324,7 @@ def get_handler(req, res)
       end
 
       def set_filename(req, res)
-        res.filename = @root.dup
+        res.filename = @root.b
         path_info = req.path_info.scan(%r|/[^/]*|)
 
         path_info.unshift("")  # dummy for checking @root dir
diff --git a/test/webrick/test_filehandler.rb b/test/webrick/test_filehandler.rb
index 33b6d7b..4d4963a 100644
--- a/test/webrick/test_filehandler.rb
+++ b/test/webrick/test_filehandler.rb
@@ -3,6 +3,7 @@
 require_relative "utils.rb"
 require "webrick"
 require "stringio"
+require "tmpdir"
 
 class WEBrick::TestFileHandler < Test::Unit::TestCase
   def teardown
@@ -285,6 +286,18 @@ def test_short_filename
     end
   end
 
+  def test_cjk_in_path
+    Dir.mktmpdir("\u3042") do |dir|
+      File.write("#{dir}/\u3042.txt", "test_cjk_in_path")
+      config = { :DocumentRoot => dir }
+      TestWEBrick.start_httpserver(config) do |server, addr, port, log|
+        http = Net::HTTP.new(addr, port)
+        req = Net::HTTP::Get.new("/%E3%81%82.txt")
+        http.request(req){|res| assert_equal("200", res.code, log.call) }
+      end
+    end
+  end
+
   def test_script_disclosure
     return if File.executable?(__FILE__) # skip on strange file system