diff --git a/ChangeLog b/ChangeLog
index 3cdf63a9cd..2c4d7ada3b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Oct 31 11:35:38 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* encoding.c (rb_enc_set_default_internal): no alias "internal" if
+	  defalt internal is not set.  [ruby-dev:37000]
+
 Fri Oct 31 21:28:14 2008  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* lib/webrick/httpauth/digestauth.rb
diff --git a/encoding.c b/encoding.c
index e9fcbfcb3e..7b7d301133 100644
--- a/encoding.c
+++ b/encoding.c
@@ -1101,8 +1101,13 @@ rb_enc_set_default_internal(VALUE encoding)
     if (default_internal_index != -2)
 	/* Already set */
 	return;
-    default_internal_index = encoding == Qnil ?
-				-1 :rb_enc_to_index(rb_to_encoding(encoding));
+    if (NIL_P(encoding)) {
+	default_internal_index = -1;
+	default_internal = 0;
+	return;
+    }
+
+    default_internal_index = rb_enc_to_index(rb_to_encoding(encoding));
     /* Convert US-ASCII => UTF-8 */
     if (default_internal_index == rb_usascii_encindex())
 	default_internal_index = rb_utf8_encindex();