Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 18567)
+++ wp-includes/functions.php	(working copy)
@@ -3799,7 +3799,7 @@
 		$cache_key = "{$wpdb->siteid}:$option";
 
 		if ( $wpdb->get_row( $wpdb->prepare( "SELECT meta_value FROM $wpdb->sitemeta WHERE meta_key = %s AND site_id = %d", $option, $wpdb->siteid ) ) )
-			return update_site_option( $option, $value );
+			return false;
 
 		$value = sanitize_option( $option, $value );
 		wp_cache_set( $cache_key, $value, 'site-options' );