--- ./devcfg.c.orig
+++ ./devcfg.c
@@ -41,6 +41,11 @@
 
 #include <assert.h>
 
+#ifndef TIOCSRS485
+#define TIOCSRS485    0x542F
+#endif
+
+
 struct devcfg_data {
     /* Information about the terminal device. */
     char           *devname;		/* The full path to the device */