diff --git a/src/Socket.h b/src/Socket.h
index e0420693..7c384af5 100644
--- a/src/Socket.h
+++ b/src/Socket.h
@@ -21,6 +21,7 @@
 #include <sys/types.h>
 
 #if defined(WIN32) || defined(WIN64)
+#include <errno.h>
 #include <winsock2.h>
 #include <ws2tcpip.h>
 #define MAXHOSTNAMELEN 256