diff --git a/ChangeLog b/ChangeLog
index 2964b117fa..5fc37e6359 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Aug 20 17:11:01 2012  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* file.c (file_path_convert): don't convert it when the path string is
+	  ascii only. [ruby-core:41556] [Bug #5733]
+	  tests are contributed by nobu.
+
 Thu Aug  9 22:48:58 2012  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* pack.c (pack_unpack): when unpack('M') occurs an illegal byte
diff --git a/file.c b/file.c
index 0310f235ca..2659ef7f6a 100644
--- a/file.c
+++ b/file.c
@@ -138,8 +138,10 @@ file_path_convert(VALUE name)
     if (rb_default_internal_encoding() != NULL
 	    && rb_usascii_encoding() != fname_encoding
 	    && rb_ascii8bit_encoding() != fname_encoding
-	    && (fs_encoding = rb_filesystem_encoding()) != fname_encoding) {
+	    && (fs_encoding = rb_filesystem_encoding()) != fname_encoding
+	    && !rb_enc_str_asciionly_p(name)) {
 	/* Don't call rb_filesystem_encoding() before US-ASCII and ASCII-8BIT */
+	/* fs_encoding should be ascii compatible */
 	name = rb_str_conv_enc(name, fname_encoding, fs_encoding);
     }
 #endif
diff --git a/test/ruby/test_econv.rb b/test/ruby/test_econv.rb
index 080d027c4a..f667d733a0 100644
--- a/test/ruby/test_econv.rb
+++ b/test/ruby/test_econv.rb
@@ -1,4 +1,5 @@
 require 'test/unit'
+require 'envutil'
 
 class TestEncodingConverter < Test::Unit::TestCase
   def check_ec(edst, esrc, eres, dst, src, ec, off, len, opts=nil)
@@ -908,4 +909,23 @@ class TestEncodingConverter < Test::Unit::TestCase
     ec2 = Encoding::Converter.new("", "", newline: :universal)
     assert_equal(ec1, ec2)
   end
+
+  def test_default_external
+    cmd = <<EOS
+    Encoding.default_external = ext = ARGV[0]
+    Encoding.default_internal = int ='utf-8'
+    begin
+      Encoding::Converter.new(ext, int)
+    ensure
+      Marshal.dump($!, STDOUT)
+      STDOUT.flush
+    end
+EOS
+    Encoding.list.grep(->(enc) {/^ISO-8859-\d(?:[0-5])?\z/i =~ enc.name}) do |enc|
+      error = IO.popen([EnvUtil.rubybin, "-e", cmd, enc.name]) do |child|
+        Marshal.load(child)
+      end
+      assert_nil(error)
+    end
+  end
 end
diff --git a/version.h b/version.h
index 241c8e2e58..bf18ef0e0d 100644
--- a/version.h
+++ b/version.h
@@ -1,10 +1,10 @@
 #define RUBY_VERSION "1.9.3"
-#define RUBY_PATCHLEVEL 260
+#define RUBY_PATCHLEVEL 261
 
-#define RUBY_RELEASE_DATE "2012-08-09"
+#define RUBY_RELEASE_DATE "2012-08-20"
 #define RUBY_RELEASE_YEAR 2012
 #define RUBY_RELEASE_MONTH 8
-#define RUBY_RELEASE_DAY 9
+#define RUBY_RELEASE_DAY 20
 
 #include "ruby/version.h"