Index: wp-includes/ms-functions.php
===================================================================
--- wp-includes/ms-functions.php	(revision 46496)
+++ wp-includes/ms-functions.php	(working copy)
@@ -1424,8 +1424,9 @@
 	 * @since MU (3.0.0)
 	 *
 	 * @param string $msg Email body.
+	 * @param int $blog_id The new site's ID.
 	 */
-	$msg = apply_filters( 'newblog_notify_siteadmin', $msg );
+	$msg = apply_filters( 'newblog_notify_siteadmin', $msg, $blog_id );
 
 	/* translators: New site notification email subject. %s: New site URL. */
 	wp_mail( $email, sprintf( __( 'New Site Registration: %s' ), $siteurl ), $msg );