diff --git a/Package.swift b/Package.swift
index 5d15a1b..0443583 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version:5.3
+// swift-tools-version:5.9
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
diff --git a/Sources/WireGuardKitC/WireGuardKitC.h b/Sources/WireGuardKitC/WireGuardKitC.h
index 54e4783..1b8974d 100644
--- a/Sources/WireGuardKitC/WireGuardKitC.h
+++ b/Sources/WireGuardKitC/WireGuardKitC.h
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: MIT
 // Copyright © 2018-2023 WireGuard LLC. All Rights Reserved.
 
+#include <sys/types.h>
 #include "key.h"
 #include "x25519.h"