Index: wordpress/wp-includes/capabilities.php
===================================================================
--- wordpress/wp-includes/capabilities.php	(revision 21261)
+++ wordpress/wp-includes/capabilities.php	(working copy)
@@ -1381,7 +1381,7 @@
  */
 function is_super_admin( $user_id = false ) {
 	if ( $user_id )
-		$user = new WP_User( $user_id );
+		$user = get_userdata( $user_id );
 	else
 		$user = wp_get_current_user();
 
Index: wordpress/wp-includes/pluggable.php
===================================================================
--- wordpress/wp-includes/pluggable.php	(revision 21261)
+++ wordpress/wp-includes/pluggable.php	(working copy)
@@ -114,7 +114,7 @@
  *
  * @since 0.71
  *
- * @param int $user_id User ID
+ * @param int $user_id User ID.
  * @return bool|object False on failure, WP_User object on success
  */
 function get_userdata( $user_id ) {
@@ -133,6 +133,9 @@
  * @return bool|object False on failure, WP_User object on success
  */
 function get_user_by( $field, $value ) {
+	if ( 'id' === $field && $value && get_current_user_id() === $value )
+		return wp_get_current_user();
+
 	$userdata = WP_User::get_data_by( $field, $value );
 
 	if ( !$userdata )