--- OLD/xc/programs/xdm/sessreg.c	Thu Jan  1 00:00:00 1970
+++ NEW/xc/programs/xdm/sessreg.c	Thu Jan  1 00:00:00 1970
@@ -44,6 +44,7 @@
 
 # include	<X11/Xos.h>
 # include	<X11/Xfuncs.h>
+#include <stdlib.h>
 # include	<stdio.h>
 # include	<utmp.h>
 
@@ -261,7 +262,8 @@
 	}
 #endif
 	if (!lflag) {
-		sysnerr ((int) (line_tmp = ttyname (0)), "ttyname");
+		line_tmp = ttyname (0);
+		if (! line_tmp) { perror("ttyname"); exit(1); }
 		line = strrchr(line_tmp, '/');
 		if (line)
 			line = line + 1;