diff --git a/lib/multi.h b/lib/multi.h
index 40010d5004..9ad8067787 100644
--- a/lib/multi.h
+++ b/lib/multi.h
@@ -50,6 +50,10 @@
 #ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
 #endif
+#ifdef HAVE_WINSOCK_H
+#include <winsock.h>
+#endif
+
 #include <curl/curl.h>
 
 typedef void CURLM;