diff --git a/lib/models/Course.class.php b/lib/models/Course.class.php
index 34b7d747645716df78394af54076365e7676fe62..1f609301e01b9b5becdb230428afd4f4e9330774 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