diff --git a/sys/netgraph7/ng_car.c b/sys/netgraph7/ng_car.c
--- a/sys/netgraph7/ng_car.c
+++ b/sys/netgraph7/ng_car.c
@@ -653,7 +653,7 @@
 {
 	int 	delay;
 
-	delay = (-(hinfo->tc)) * hz * 8 / hinfo->conf.cir + 1;
+	delay = (hinfo->conf.cir == 0) ? 0 : (-(hinfo->tc)) * hz * 8 / hinfo->conf.cir + 1;
 
 	ng_callout(&hinfo->q_callout, NG_HOOK_NODE(hinfo->hook), hinfo->hook,
 	    delay, &ng_car_q_event, NULL, 0);