diff --git a/koha-tmpl/intranet-tmpl/prog/js/pages/preferences.js b/koha-tmpl/intranet-tmpl/prog/js/pages/preferences.js
index fb63d4b397..f5da1d92c4 100644
--- a/koha-tmpl/intranet-tmpl/prog/js/pages/preferences.js
+++ b/koha-tmpl/intranet-tmpl/prog/js/pages/preferences.js
@@ -13,7 +13,7 @@ KOHA.Preferences = {
         // If a multiple select has all its entries unselected
         var unserialized = new Array();
         $(modified_prefs).each(function(){
-            if ( $(this).attr('multiple') && $(this).val() == null ) {
+            if ( $(this).attr('multiple') && $(this).val().length == 0 ) {
                 unserialized.push($(this));
             }
         });