diff --git a/sys/netinet/sctp_cc_functions.c b/sys/netinet/sctp_cc_functions.c
index d788ff2ffcda..e32faf95a0cf 100644
--- a/sys/netinet/sctp_cc_functions.c
+++ b/sys/netinet/sctp_cc_functions.c
@@ -1130,12 +1130,9 @@ sctp_cwnd_update_after_packet_dropped(struct sctp_tcb *stcb,
     uint32_t * bottle_bw, uint32_t * on_queue)
 {
 	uint32_t bw_avail;
-	int rtt;
 	unsigned int incr;
 	int old_cwnd = net->cwnd;
 
-	/* need real RTT in msd for this calc */
-	rtt = net->rtt / 1000;
 	/* get bottle neck bw */
 	*bottle_bw = ntohl(cp->bottle_bw);
 	/* and whats on queue */
@@ -1144,10 +1141,11 @@ sctp_cwnd_update_after_packet_dropped(struct sctp_tcb *stcb,
 	 * adjust the on-queue if our flight is more it could be that the
 	 * router has not yet gotten data "in-flight" to it
 	 */
-	if (*on_queue < net->flight_size)
+	if (*on_queue < net->flight_size) {
 		*on_queue = net->flight_size;
-	/* calculate the available space */
-	bw_avail = (*bottle_bw * rtt) / 1000;
+	}
+	/* rtt is measured in micro seconds, bottle_bw in bytes per second */
+	bw_avail = (uint32_t) (((uint64_t) (*bottle_bw) * net->rtt) / (uint64_t) 1000000);
 	if (bw_avail > *bottle_bw) {
 		/*
 		 * Cap the growth to no more than the bottle neck. This can
@@ -1167,7 +1165,6 @@ sctp_cwnd_update_after_packet_dropped(struct sctp_tcb *stcb,
 		int seg_inflight, seg_onqueue, my_portion;
 
 		net->partial_bytes_acked = 0;
-
 		/* how much are we over queue size? */
 		incr = *on_queue - bw_avail;
 		if (stcb->asoc.seen_a_sack_this_pkt) {