diff --git a/calendar/classes/external/calendar_day_exporter.php b/calendar/classes/external/calendar_day_exporter.php
index fac496aaaf6..5869c109bf8 100644
--- a/calendar/classes/external/calendar_day_exporter.php
+++ b/calendar/classes/external/calendar_day_exporter.php
@@ -74,7 +74,7 @@ class calendar_day_exporter extends exporter {
             ],
             'defaulteventcontext' => [
                 'type' => PARAM_INT,
-                'default' => null,
+                'default' => 0,
             ],
             'filter_selector' => [
                 'type' => PARAM_RAW,
diff --git a/calendar/classes/external/calendar_upcoming_exporter.php b/calendar/classes/external/calendar_upcoming_exporter.php
index ab35779aa4c..a7759c678cb 100644
--- a/calendar/classes/external/calendar_upcoming_exporter.php
+++ b/calendar/classes/external/calendar_upcoming_exporter.php
@@ -74,7 +74,7 @@ class calendar_upcoming_exporter extends exporter {
             ],
             'defaulteventcontext' => [
                 'type' => PARAM_INT,
-                'default' => null,
+                'default' => 0,
             ],
             'filter_selector' => [
                 'type' => PARAM_RAW,
diff --git a/calendar/classes/external/month_exporter.php b/calendar/classes/external/month_exporter.php
index 9ca253e8ae5..12b910ee0bf 100644
--- a/calendar/classes/external/month_exporter.php
+++ b/calendar/classes/external/month_exporter.php
@@ -171,7 +171,7 @@ class month_exporter extends exporter {
             ],
             'defaulteventcontext' => [
                 'type' => PARAM_INT,
-                'default' => null,
+                'default' => 0,
             ],
         ];
     }