diff --git a/ChangeLog b/ChangeLog
index 6f0d63ef39..d5a8a6cb83 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,7 @@
-Wed Dec 26 07:31:19 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Wed Dec 26 07:31:24 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* string.c (rb_enc_cr_str_copy_for_substr): empty string is always
+	  valid or 7bit.
 
 	* string.c (rb_str_enumerate_lines, rb_str_chop): reduce duplicated
 	  code.
diff --git a/string.c b/string.c
index 26af8b613f..a3f937d19e 100644
--- a/string.c
+++ b/string.c
@@ -293,6 +293,13 @@ rb_enc_cr_str_copy_for_substr(VALUE dest, VALUE src)
      * from src to new string "dest" which is made from the part of src.
      */
     str_enc_copy(dest, src);
+    if (RSTRING_LEN(dest) == 0) {
+	if (!rb_enc_asciicompat(STR_ENC_GET(src)))
+	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_VALID);
+	else
+	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
+	return;
+    }
     switch (ENC_CODERANGE(src)) {
       case ENC_CODERANGE_7BIT:
 	ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
@@ -305,12 +312,6 @@ rb_enc_cr_str_copy_for_substr(VALUE dest, VALUE src)
 	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
 	break;
       default:
-	if (RSTRING_LEN(dest) == 0) {
-	    if (!rb_enc_asciicompat(STR_ENC_GET(src)))
-		ENC_CODERANGE_SET(dest, ENC_CODERANGE_VALID);
-	    else
-		ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
-	}
 	break;
     }
 }