diff --git a/include/ac/socket.h b/include/ac/socket.h
index 073b10744a..7d345c0461 100644
--- a/include/ac/socket.h
+++ b/include/ac/socket.h
@@ -99,6 +99,7 @@
 #	endif
 
 #undef EWOULDBLOCK
+#undef ENOTCONN
 #undef EINPROGRESS
 #undef ETIMEDOUT
 #define EWOULDBLOCK WSAEWOULDBLOCK