diff --git a/index.d.ts b/index.d.ts
index 9ad9399..04006c0 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -60,6 +60,13 @@ export function writeChecksum(
 
 export function createChecksum(...args: Buffer[]): number;
 
+export interface TAddressFamily {
+  IPv4: number;
+  IPv6: number;
+}
+
+export const AddressFamily: TAddressFamily;
+
 export interface TProtocol {
   ICMP: number;
   TCP: number;