diff --git a/theme/bootstrapbase/renderers/core_renderer.php b/theme/bootstrapbase/renderers/core_renderer.php
index 1ccc13b3261..75f7b7a7424 100644
--- a/theme/bootstrapbase/renderers/core_renderer.php
+++ b/theme/bootstrapbase/renderers/core_renderer.php
@@ -78,8 +78,8 @@ class theme_bootstrapbase_core_renderer extends core_renderer {
     public function custom_menu($custommenuitems = '') {
         global $CFG;
 
-        if (!empty($CFG->custommenuitems)) {
-            $custommenuitems .= $CFG->custommenuitems;
+        if (empty($custommenuitems) && !empty($CFG->custommenuitems)) {
+            $custommenuitems = $CFG->custommenuitems;
         }
         $custommenu = new custom_menu($custommenuitems, current_language());
         return $this->render_custom_menu($custommenu);