#define WAKE_EVENT(s) (write ((s)->control_write_fd.fd, "W", 1) == 1)
#define RELEASE_EVENT(s) (read ((s)->control_read_fd.fd, (s)->buf, 1) == 1)
#else
-#define WAKE_EVENT(s) (SetEvent ((s)->wakeup_event), errno = GetLastError () == NO_ERROR ? 0 : EACCES, errno == 0 ? 1 : 0)
+#define WAKE_EVENT(s) (SetLastError (0), SetEvent ((s)->wakeup_event), errno = GetLastError () == NO_ERROR ? 0 : EACCES, errno == 0 ? 1 : 0)
#define RELEASE_EVENT(s) (ResetEvent ((s)->wakeup_event))
#endif