diff --git a/lib/private-libwebsockets.h b/lib/private-libwebsockets.h
index 6900fd21a..6b897f0bc 100644
--- a/lib/private-libwebsockets.h
+++ b/lib/private-libwebsockets.h
@@ -66,6 +66,9 @@
 #ifndef EINPROGRESS
 #define EINPROGRESS WSAEINPROGRESS
 #endif
+#ifndef EISCONN
+#define EISCONN WSAEISCONN
+#endif
 
 #define compatible_close(fd) closesocket(fd);
 #ifdef __MINGW64__