diff --git a/include/mswsock.h b/include/mswsock.h
index 322ab201343..1447a8d127a 100644
--- a/include/mswsock.h
+++ b/include/mswsock.h
@@ -84,8 +84,10 @@ extern "C" {
 
 #ifndef USE_WS_PREFIX
 #define SIO_UDP_CONNRESET _WSAIOW(IOC_VENDOR,12)
+#define SIO_SET_COMPATIBILITY_MODE _WSAIOW(IOC_VENDOR,300)
 #else
 #define WS_SIO_UDP_CONNRESET _WSAIOW(WS_IOC_VENDOR,12)
+#define WS_SIO_SET_COMPATIBILITY_MODE _WSAIOW(IOC_VENDOR,300)
 #endif
 
 #define DE_REUSE_SOCKET TF_REUSE_SOCKET