Index: src/OFTCPSocket.m
==================================================================
--- src/OFTCPSocket.m
+++ src/OFTCPSocket.m
@@ -14,10 +14,11 @@
  * file.
  */
 
 #include "config.h"
 
+#define _WIN32_WINNT 0x0501
 #define __NO_EXT_QNX
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>