diff --git a/mod/forum/classes/local/exporters/post.php b/mod/forum/classes/local/exporters/post.php
index e9c445ed7ac..eed547a4818 100644
--- a/mod/forum/classes/local/exporters/post.php
+++ b/mod/forum/classes/local/exporters/post.php
@@ -105,8 +105,16 @@ class post extends exporter {
                 'default' => null,
                 'null' => NULL_ALLOWED
             ],
-            'timecreated' => ['type' => PARAM_INT],
-            'timemodified' => ['type' => PARAM_INT],
+            'timecreated' => [
+                'type' => PARAM_INT,
+                'default' => null,
+                'null' => NULL_ALLOWED
+            ],
+            'timemodified' => [
+                'type' => PARAM_INT,
+                'default' => null,
+                'null' => NULL_ALLOWED
+            ],
             'unread' => [
                 'type' => PARAM_BOOL,
                 'optional' => true,