diff --git a/lib/models/Course.class.php b/lib/models/Course.class.php
index 3f635d71a9805b3dfcc6f88f0752e0d57976f675..8bca5e9058cf7118ef647860b9f98e20503eef30 100644
--- a/lib/models/Course.class.php
+++ b/lib/models/Course.class.php
@@ -1110,7 +1110,7 @@ class Course extends SimpleORMap implements Range, PrivacyObject, StudipItem, Fe
     public function isCalendarWritable(string $user_id = null): bool
     {
         if ($user_id === null) {
-            $user_id = self::findCurrent()->id;
+            $user_id = User::findCurrent()->id;
         }
 
         //Calendar write permissions are granted for all participants