diff --git a/ChangeLog b/ChangeLog
index ad79809812..400f3cdb0b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Feb 22 21:12:42 2008  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* string.c (rb_enc_cr_str_copy): check string's coderange is 7bit or
+	  valid.
+
 Fri Feb 22 19:50:19 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* bignum.c (BIGZEROP): fix for longer Bignum zeros.  [ruby-Bugs-17454]
diff --git a/string.c b/string.c
index 90ed51b108..da7eba3cba 100644
--- a/string.c
+++ b/string.c
@@ -215,8 +215,17 @@ void
 rb_enc_cr_str_copy(VALUE dest, VALUE src)
 {
     rb_enc_copy(dest, src);
-    if (!is_broken_string(src))
-	ENC_CODERANGE_SET(dest, ENC_CODERANGE(src));
+    switch (ENC_CODERANGE(src)) {
+    case ENC_CODERANGE_7BIT:
+	ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
+	break;
+    case ENC_CODERANGE_VALID:
+	if (search_nonascii(RSTRING_PTR(dest), RSTRING_END(dest)))
+	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_VALID);
+	else
+	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
+	break;
+    }
 }
 
 void