diff --git a/include/ac/socket.h b/include/ac/socket.h
index a80254120f..5d739920c6 100644
--- a/include/ac/socket.h
+++ b/include/ac/socket.h
@@ -99,6 +99,7 @@
 #	endif
 
 #define EWOULDBLOCK WSAEWOULDBLOCK
+#define ENOTCONN WSAENOTCONN
 #define EINPROGRESS WSAEINPROGRESS
 #define ETIMEDOUT	WSAETIMEDOUT