diff --git a/main/template/default/layout/header.js.tpl b/main/template/default/layout/header.js.tpl
index d8c460deba..603227b215 100644
--- a/main/template/default/layout/header.js.tpl
+++ b/main/template/default/layout/header.js.tpl
@@ -138,7 +138,7 @@ $(document).ready(function() {
 
             modalDialog.removeClass('modal-lg modal-sm').css('width', '');
 
-            if (modalSize) {
+            if (modalSize && modalSize.length != 0) {
                 switch (modalSize) {
                     case 'lg':
                         modalDialog.addClass('modal-lg');