diff --git a/ChangeLog b/ChangeLog
index 82ae100391..44e3d8571e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Tue Jun 17 06:26:28 2008  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* encoding.c (rb_filesystem_encoding): defined.
+
+	* include/ruby/encoding.h (rb_filesystem_encoding): added.
+
 Tue Jun 17 06:24:28 2008  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* ext/syck/rubyext.c: add encoding header.
diff --git a/encoding.c b/encoding.c
index 0928b4b2b0..305213569c 100644
--- a/encoding.c
+++ b/encoding.c
@@ -962,6 +962,22 @@ rb_locale_encoding(void)
     return rb_enc_from_index(idx);
 }
 
+rb_encoding *
+rb_filesystem_encoding(void)
+{
+    static rb_encoding *enc;
+    if (!enc) {
+#if defined _WIN32
+	enc = rb_locale_encoding();
+#elif defined __APPLE__
+	enc = rb_enc_find("UTF8-MAC");
+#else
+	enc = rb_ascii8bit_encoding();
+#endif
+    }
+    return enc;
+}
+
 static int default_external_index;
 
 rb_encoding *
diff --git a/include/ruby/encoding.h b/include/ruby/encoding.h
index 1955a4f205..33a8fcd73e 100644
--- a/include/ruby/encoding.h
+++ b/include/ruby/encoding.h
@@ -165,6 +165,7 @@ rb_encoding *rb_ascii8bit_encoding(void);
 rb_encoding *rb_utf8_encoding(void);
 rb_encoding *rb_usascii_encoding(void);
 rb_encoding *rb_locale_encoding(void);
+rb_encoding *rb_filesystem_encoding(void);
 rb_encoding *rb_default_external_encoding(void);
 int rb_usascii_encindex(void);
 int rb_ascii8bit_encindex(void);