From 9d6a989a46c453463a98894e02aa0578907b2fe0 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Fri, 29 Apr 1994 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1994-04-29

---
 port/alarm.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/port/alarm.c b/port/alarm.c
index 338c5ca94f503c0525b0cba7d98846d7cb4f15c3..2cd83286340de40b4fde4070b73f4935334ddeec 100644
--- a/port/alarm.c
+++ b/port/alarm.c
@@ -84,7 +84,10 @@ procalarm(ulong time)
 	Proc **l, *f;
 	ulong when, old;
 
-	old = TK2MS(up->alarm - MACHP(0)->ticks);
+	if(up->alarm)
+		old = TK2MS(up->alarm - MACHP(0)->ticks);
+	else
+		old = 0;
 	if(time == 0) {
 		up->alarm = 0;
 		return old;