diff --git a/lib/classes/event/calendar_event_created.php b/lib/classes/event/calendar_event_created.php
index 399b943aae1..28c47a07e71 100644
--- a/lib/classes/event/calendar_event_created.php
+++ b/lib/classes/event/calendar_event_created.php
@@ -107,7 +107,7 @@ class calendar_event_created extends base {
         if (empty($this->other['name'])) {
             throw new \coding_exception('The \'name\' value must be set in other.');
         }
-        if (empty($this->other['timestart'])) {
+        if (!isset($this->other['timestart'])) {
             throw new \coding_exception('The \'timestart\' value must be set in other.');
         }
     }
diff --git a/lib/classes/event/calendar_event_deleted.php b/lib/classes/event/calendar_event_deleted.php
index 4de8aa04a11..933f0b075dc 100644
--- a/lib/classes/event/calendar_event_deleted.php
+++ b/lib/classes/event/calendar_event_deleted.php
@@ -88,7 +88,7 @@ class calendar_event_deleted extends base {
         if (empty($this->other['name'])) {
             throw new \coding_exception('The \'name\' value must be set in other.');
         }
-        if (empty($this->other['timestart'])) {
+        if (!isset($this->other['timestart'])) {
             throw new \coding_exception('The \'timestart\' value must be set in other.');
         }
     }