diff --git a/components/ILIAS/Calendar/classes/class.ilCalendarPresentationGUI.php b/components/ILIAS/Calendar/classes/class.ilCalendarPresentationGUI.php
index f4798e6151e7..c9292ee30e05 100755
--- a/components/ILIAS/Calendar/classes/class.ilCalendarPresentationGUI.php
+++ b/components/ILIAS/Calendar/classes/class.ilCalendarPresentationGUI.php
@@ -211,7 +211,9 @@ public function executeCommand(): void
         }
 
         $this->initSeed();
-        $this->prepareOutput();
+        if (!$this->ctrl->isAsynch()) {
+            $this->prepareOutput();
+        }
 
         $this->help->setScreenIdComponent("cal");
         switch ($cmd) {