diff --git a/ChangeLog b/ChangeLog
index 9057898b15..0f6fc95461 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat Sep 20 07:59:31 2008  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* re.c (rb_reg_desc): Regexps of ASCII Compatible encoding may
+	  contain non-ASCII characters. So in that case its encoding
+	  must keep original encoding.
+
 Sat Sep 20 07:44:56 2008  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* common.mk: prec.c is removed.
diff --git a/re.c b/re.c
index b9d3840313..9b9cb87d02 100644
--- a/re.c
+++ b/re.c
@@ -380,8 +380,12 @@ static VALUE
 rb_reg_desc(const char *s, long len, VALUE re)
 {
     VALUE str = rb_str_buf_new2("/");
-
-    rb_enc_associate(str, rb_usascii_encoding());
+    if (rb_enc_asciicompat(rb_enc_get(re))) {
+	rb_enc_copy(str, re);
+    }
+    else {
+	rb_enc_associate(str, rb_usascii_encoding());
+    }
     rb_reg_expr_str(str, s, len);
     rb_str_buf_cat2(str, "/");
     if (re) {