diff --git a/application/Calendar/CalendarModel.php b/application/Calendar/CalendarModel.php
index d3fe6f931..d74abce7f 100644
--- a/application/Calendar/CalendarModel.php
+++ b/application/Calendar/CalendarModel.php
@@ -265,9 +265,10 @@ class CalendarModel
                     continue;
                 }
                 if ($data['all_day_event'] == 1) {
-                    if (in_array("Feiertag", $categories)) {
+                    if (is_array($categories) && in_array("Feiertag", $categories)) {
                         continue;
                     }
+
                     $starttime = date("Y-m-d", $data['start_time']);
                     $endtime = date("Y-m-d", $data['end_time']);
                 } else {