diff --git a/phpBB/docs/CHANGELOG.html b/phpBB/docs/CHANGELOG.html
index 9d85cdc5a5..8355dbf1e1 100644
--- a/phpBB/docs/CHANGELOG.html
+++ b/phpBB/docs/CHANGELOG.html
@@ -89,6 +89,7 @@
 		<li>[Fix] Allow mixed-case template directories to be inherited (Bug #36725)</li>
 		<li>[Fix] Regression bug from revision #8908 regarding log display in ACP</li>
 		<li>[Fix] Allow the UCP group management to work for groups with avatars. (Bug #37375)</li>
+		<li>[Fix] Fix header list build for replying oldest PM in PM history (Bug #37275)</li>
 	</ul>
 
 	<a name="v302"></a><h3>1.ii. Changes since 3.0.2</h3>
diff --git a/phpBB/includes/ucp/ucp_pm_compose.php b/phpBB/includes/ucp/ucp_pm_compose.php
index 060baaefa0..ba06315363 100644
--- a/phpBB/includes/ucp/ucp_pm_compose.php
+++ b/phpBB/includes/ucp/ucp_pm_compose.php
@@ -424,7 +424,9 @@ function compose_pm($id, $mode, $action)
 	{
 		// We try to include every previously listed member from the TO Header
 		$list = rebuild_header(array('to' => $post['to_address']));
-		$list = $list['u'];
+
+		// Can be an empty array too ;)
+		$list = (!empty($list['u'])) ? $list['u'] : array();
 		$list[$post['author_id']] = 'to';
 
 		if (isset($list[$user->data['user_id']]))