diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index ba52832..7228d30 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -252,9 +252,9 @@
 static unsigned int netem_drop(struct Qdisc* sch)
 {
 	struct netem_sched_data *q = qdisc_priv(sch);
-	unsigned int len;
+	unsigned int len = 0;
 
-	if ((len = q->qdisc->ops->drop(q->qdisc)) != 0) {
+	if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
 		sch->q.qlen--;
 		sch->qstats.drops++;
 	}
diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
index 1641db3..3395ca7 100644
--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -165,7 +165,7 @@
 
 	for (prio = q->bands-1; prio >= 0; prio--) {
 		qdisc = q->queues[prio];
-		if ((len = qdisc->ops->drop(qdisc)) != 0) {
+		if (qdisc->ops->drop && (len = qdisc->ops->drop(qdisc)) != 0) {
 			sch->q.qlen--;
 			return len;
 		}
diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index cb9711e..e9e4734 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -177,9 +177,9 @@
 static unsigned int tbf_drop(struct Qdisc* sch)
 {
 	struct tbf_sched_data *q = qdisc_priv(sch);
-	unsigned int len;
+	unsigned int len = 0;
 
-	if ((len = q->qdisc->ops->drop(q->qdisc)) != 0) {
+	if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
 		sch->q.qlen--;
 		sch->qstats.drops++;
 	}