diff --git a/lib/connect.c b/lib/connect.c
index 277e1dfaee..c045ba436b 100644
--- a/lib/connect.c
+++ b/lib/connect.c
@@ -61,6 +61,7 @@
 #include <winsock.h>
 #define EINPROGRESS WSAEINPROGRESS
 #define EWOULDBLOCK WSAEWOULDBLOCK
+#define EISCONN     WSAEISCONN
 #endif
 
 #include "urldata.h"