diff -Naur -X exclude-files ac_clean/arch/um/drivers/chan_kern.c ac/arch/um/drivers/chan_kern.c
--- ac_clean/arch/um/drivers/chan_kern.c	Sun May 27 15:42:43 2001
+++ ac/arch/um/drivers/chan_kern.c	Sun May 27 18:19:20 2001
@@ -17,7 +17,7 @@
 
 	if(count == 0) return;
 	n = tty_read(&chan->in, tty);
-	tty_flip_buffer_push(tty);
+	if(tty) tty_flip_buffer_push(tty);
 	if(n > 0) chan->in.hung_up = 0;
 	if(n >= 0) reactivate_fd(chan->in.fd);
 }