diff --git a/libs/midi++2/ipmidi_port.cc b/libs/midi++2/ipmidi_port.cc
index 297ad894f7..59606bffb2 100644
--- a/libs/midi++2/ipmidi_port.cc
+++ b/libs/midi++2/ipmidi_port.cc
@@ -25,6 +25,10 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
+#ifdef   COMPILER_MSVC
+#undef   O_NONBLOCK
+#define  O_NONBLOCK 0
+#endif
 #if defined(WIN32)
 #include <winsock2.h>
 #else