--- a/include/grpc/event_engine/port.h	(index)
+++ b/include/grpc/event_engine/port.h	(working tree)
@@ -31,6 +31,13 @@
 #include <winsock2.h>
 #include <ws2tcpip.h>
 // must be included after the above
+
+// For some reason OPTIONAL is not defined and build for window is not OK
+// Let, define it here as empty
+#ifndef OPTIONAL
+#define OPTIONAL
+#endif
+
 #include <mswsock.h>
 #else
 #error UNKNOWN PLATFORM