diff --git a/adminer/include/auth.inc.php b/adminer/include/auth.inc.php
index 1051186f..964f1d90 100644
--- a/adminer/include/auth.inc.php
+++ b/adminer/include/auth.inc.php
@@ -162,7 +162,7 @@ stop_session(true);
 
 if (isset($_GET["username"]) && is_string(get_password())) {
 	list($host, $port) = explode(":", SERVER, 2);
-	if (is_numeric($port) && ($port < 1024 || $port > 65535)) {
+	if (+$port && ($port < 1024 || $port > 65535)) {
 		auth_error(lang('Connecting to privileged ports is not allowed.'));
 	}
 	check_invalid_login();
diff --git a/changes.txt b/changes.txt
index 11ddd26a..a8dd5798 100644
--- a/changes.txt
+++ b/changes.txt
@@ -1,5 +1,6 @@
 Adminer 4.7.8-dev:
 Support PHP 8
+Disallow connecting to privileged ports (bug #769)
 
 Adminer 4.7.7 (released 2020-05-11):
 Fix open redirect if Adminer is accessible at //adminer.php%2F@