diff --git a/ixwebsocket/IXNetSystem.h b/ixwebsocket/IXNetSystem.h
index 21131b4..7ca58f4 100644
--- a/ixwebsocket/IXNetSystem.h
+++ b/ixwebsocket/IXNetSystem.h
@@ -17,6 +17,7 @@
 #include <basetsd.h>
 #include <io.h>
 #include <ws2def.h>
+#include <cerrno>
 
 #undef EWOULDBLOCK
 #undef EAGAIN