diff --git a/bt/announce.php b/bt/announce.php
index db2127e53..ee50b5b67 100644
--- a/bt/announce.php
+++ b/bt/announce.php
@@ -100,12 +100,21 @@ $info_hash_hex = bin2hex($info_hash);
 // Store peer id
 $peer_id_sql = preg_replace('/[^a-zA-Z0-9\-\_]/', '', $peer_id);
 
+// Stopped event
+$stopped = ($event === 'stopped');
+
 // Check info_hash length
 if (strlen($info_hash) !== 20) {
     msg_die('Invalid info_hash: ' . (mb_check_encoding($info_hash, 'UTF8') ? $info_hash : $info_hash_hex));
 }
 
-if (!isset($port) || $port < 0 || $port > 0xFFFF) {
+if (
+    // https://github.com/HDInnovations/UNIT3D-Community-Edition/blob/c64275f0b5dcb3c4c845d5204871adfe24f359d6/app/Http/Controllers/AnnounceController.php#L284
+    // Block system-reserved ports since 99.9% of the time they're fake and thus not connectable
+    // Some clients will send port of 0 on 'stopped' events. Let them through as they won't receive peers anyway.
+    !isset($port)
+    || ($port < 1024 && !$stopped)
+    || $port > 0xFFFF) {
     msg_die('Invalid port: ' . $port);
 }
 
@@ -158,9 +167,6 @@ if ($ip_version === 'ipv6') {
 // Peer unique id
 $peer_hash = hash('xxh128', $passkey . $info_hash_hex . $port);
 
-// Events
-$stopped = ($event === 'stopped');
-
 // Set seeder & complete
 $complete = $seeder = ($left == 0) ? 1 : 0;