diff --git a/src/lib/empthread/ntthread.c b/src/lib/empthread/ntthread.c
index 38e43c51..8412bbfd 100644
--- a/src/lib/empthread/ntthread.c
+++ b/src/lib/empthread/ntthread.c
@@ -53,6 +53,7 @@
 #include "prototypes.h"
 
 #if defined(_WIN32) && defined(_EMPTH_WIN32)
+#define WIN32
 #include <winsock2.h>
 #undef NS_ALL
 #include <windows.h>
diff --git a/src/lib/gen/io.c b/src/lib/gen/io.c
index 78121b27..983eccb1 100644
--- a/src/lib/gen/io.c
+++ b/src/lib/gen/io.c
@@ -52,6 +52,7 @@
 #include <stdlib.h>		/* malloc calloc free */
 
 #if defined(_WIN32)
+#define WIN32
 #include <winsock2.h>
 #undef NS_ALL
 #endif
diff --git a/src/lib/player/accept.c b/src/lib/player/accept.c
index c74c4762..8460e95d 100644
--- a/src/lib/player/accept.c
+++ b/src/lib/player/accept.c
@@ -32,6 +32,7 @@
  */
 
 #if defined(_WIN32)
+#define WIN32
 #include <winsock2.h>
 #undef NS_ALL
 #endif
diff --git a/src/server/main.c b/src/server/main.c
index 1492c878..27862cfb 100644
--- a/src/server/main.c
+++ b/src/server/main.c
@@ -43,6 +43,7 @@
 #include <string.h>
 
 #if defined(_WIN32)
+#define WIN32
 #include <winsock2.h>
 #undef NS_ALL
 #include <process.h>