diff --git a/ChangeLog b/ChangeLog
index 8a60f934f3..47d50ebece 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Jan 24 01:00:34 2008  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* encoding.{c, h} (rb_usascii_encoding): added.
+
 Wed Jan 23 23:54:40 2008  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* sprintf.c: fix comment.  [ruby-dev:33275]
diff --git a/encoding.c b/encoding.c
index 10e3b3a44c..bddae485b9 100644
--- a/encoding.c
+++ b/encoding.c
@@ -984,6 +984,15 @@ rb_utf8_encoding(void)
     return enc_table.list[ENCINDEX_UTF_8].enc;
 }
 
+rb_encoding *
+rb_usascii_encoding(void)
+{
+    if (!enc_table.list) {
+	rb_enc_init();
+    }
+    return enc_table.list[ENCINDEX_US_ASCII].enc;
+}
+
 rb_encoding *
 rb_locale_encoding(void)
 {
diff --git a/include/ruby/encoding.h b/include/ruby/encoding.h
index fad89a6da8..27abba1d53 100644
--- a/include/ruby/encoding.h
+++ b/include/ruby/encoding.h
@@ -160,6 +160,7 @@ int rb_enc_str_asciionly_p(VALUE);
 VALUE rb_enc_from_encoding(rb_encoding *enc);
 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_default_external_encoding(void);
 VALUE rb_enc_default_external(void);