diff --git a/plugins/kolab_notes/kolab_notes_ui.php b/plugins/kolab_notes/kolab_notes_ui.php
index 99cce46a..f180f50a 100644
--- a/plugins/kolab_notes/kolab_notes_ui.php
+++ b/plugins/kolab_notes/kolab_notes_ui.php
@@ -79,13 +79,14 @@ class kolab_notes_ui
         }
 
         $lang_codes = array($_SESSION['language']);
+        $assets_dir = $this->rc->config->get('assets_dir') ?: INSTALL_PATH;
 
         if ($pos = strpos($_SESSION['language'], '_')) {
             $lang_codes[] = substr($_SESSION['language'], 0, $pos);
         }
 
         foreach ($lang_codes as $code) {
-            if (file_exists(INSTALL_PATH . "program/js/tinymce/langs/$code.js")) {
+            if (file_exists("$assets_dir/program/js/tinymce/langs/$code.js")) {
                 $lang = $code;
                 break;
             }