diff --git a/ChangeLog b/ChangeLog
index 0af61047a0..02e1c31d6b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Feb 15 10:35:54 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* re.c (rb_reg_quote): set US-ACII for ASCII-only string.
+	  [ruby-dev:33785]
+
 Fri Feb 15 10:27:47 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* {win,bcc}32/Makefile.sub (config.h): added HAVE_FTRUNCATE.
diff --git a/re.c b/re.c
index cd93024302..4867104250 100644
--- a/re.c
+++ b/re.c
@@ -2540,7 +2540,7 @@ rb_reg_quote(VALUE str)
     }
     if (ascii_only && rb_enc_get_index(str) != 0) {
         str = rb_str_new3(str);
-        rb_enc_associate(str, rb_ascii8bit_encoding());
+        rb_enc_associate(str, rb_usascii_encoding());
     }
     return str;