diff --git a/ext/ftp/php_ftp.c b/ext/ftp/php_ftp.c
index 56938459bb33..9a4785924567 100644
--- a/ext/ftp/php_ftp.c
+++ b/ext/ftp/php_ftp.c
@@ -145,6 +145,11 @@ PHP_FUNCTION(ftp_connect)
 		RETURN_THROWS();
 	}
 
+	if (port < 0 || port > 65535) {
+		zend_argument_value_error(2, "must be between 0 and 65535");
+		RETURN_THROWS();
+	}
+
 	if (timeout_sec <= 0) {
 		zend_argument_value_error(3, "must be greater than 0");
 		RETURN_THROWS();
@@ -187,6 +192,11 @@ PHP_FUNCTION(ftp_ssl_connect)
 		RETURN_THROWS();
 	}
 
+	if (port < 0 || port > 65535) {
+		zend_argument_value_error(2, "must be between 0 and 65535");
+		RETURN_THROWS();
+	}
+
 	if (timeout_sec <= 0) {
 		zend_argument_value_error(3, "must be greater than 0");
 		RETURN_THROWS();
diff --git a/ext/ftp/tests/ftp_connect_port_range.phpt b/ext/ftp/tests/ftp_connect_port_range.phpt
new file mode 100644
index 000000000000..4225c07cd00f
--- /dev/null
+++ b/ext/ftp/tests/ftp_connect_port_range.phpt
@@ -0,0 +1,31 @@
+--TEST--
+ftp_connect(): $port values outside 0-65535 must throw ValueError, not alias onto a valid port
+--EXTENSIONS--
+ftp
+--FILE--
+<?php
+foreach ([-1, 65536, 65536 + 2121, PHP_INT_MIN, PHP_INT_MAX] as $port) {
+    try {
+        ftp_connect('127.0.0.1', $port);
+    } catch (ValueError $e) {
+        echo $e->getMessage(), "\n";
+    }
+}
+
+// Port 0 must be accepted (maps to default FTP port 21 in ftp_open)
+// We expect false (connection refused), not ValueError.
+$result = @ftp_connect('127.0.0.1', 0);
+var_dump($result === false || is_object($result)); // true either way
+
+// Port 65535 must be accepted (last valid port).
+$result = @ftp_connect('127.0.0.1', 65535);
+var_dump($result === false || is_object($result)); // true either way
+?>
+--EXPECT--
+ftp_connect(): Argument #2 ($port) must be between 0 and 65535
+ftp_connect(): Argument #2 ($port) must be between 0 and 65535
+ftp_connect(): Argument #2 ($port) must be between 0 and 65535
+ftp_connect(): Argument #2 ($port) must be between 0 and 65535
+ftp_connect(): Argument #2 ($port) must be between 0 and 65535
+bool(true)
+bool(true)