diff --git a/include/windns.h b/include/windns.h
index 85f38db68c6..1b1a4e13427 100644
--- a/include/windns.h
+++ b/include/windns.h
@@ -163,6 +163,13 @@ typedef struct
     DWORD IP6Dword[4];
 } IP6_ADDRESS, *PIP6_ADDRESS, DNS_IP6_ADDRESS, *PDNS_IP6_ADDRESS;
 
+#define SIZEOF_IP4_ADDRESS                   4
+#define IP4_ADDRESS_STRING_LENGTH           16
+#define IP6_ADDRESS_STRING_LENGTH           65
+#define DNS_ADDRESS_STRING_LENGTH           IP6_ADDRESS_STRING_LENGTH
+#define IP4_ADDRESS_STRING_BUFFER_LENGTH    IP4_ADDRESS_STRING_LENGTH
+#define IP6_ADDRESS_STRING_BUFFER_LENGTH    IP6_ADDRESS_STRING_LENGTH
+
 typedef struct _IP4_ARRAY
 {
     DWORD AddrCount;