Include GUSI.h if compiling for mac with gusi-sockets
diff --git a/Include/myselect.h b/Include/myselect.h
index ee964eb..0c92c7a 100644
--- a/Include/myselect.h
+++ b/Include/myselect.h
@@ -44,6 +44,11 @@
 
 #else /* !HAVE_SYS_SELECT_H */
 
+#ifdef USE_GUSI
+/* If we don't have sys/select the definition may be in unistd.h */
+#include <GUSI.h>
+#endif
+
 #include "mytime.h"
 
 #endif /* !HAVE_SYS_SELECT_H */