diff --git a/lib/route/qdisc/tbf.c b/lib/route/qdisc/tbf.c
index eb574d9..d2416bc 100644
--- a/lib/route/qdisc/tbf.c
+++ b/lib/route/qdisc/tbf.c
@@ -54,13 +54,13 @@ static int tbf_msg_parser(struct rtnl_tc *tc, void *data)
 	
 		rtnl_copy_ratespec(&tbf->qt_rate, &opts.rate);
 		tbf->qt_rate_txtime = opts.buffer;
-		bufsize = rtnl_tc_calc_bufsize(nl_ticks2us(opts.buffer),
+		bufsize = rtnl_tc_calc_bufsize(tbf->qt_rate_txtime,
 					       opts.rate.rate);
 		tbf->qt_rate_bucket = bufsize;
 
 		rtnl_copy_ratespec(&tbf->qt_peakrate, &opts.peakrate);
 		tbf->qt_peakrate_txtime = opts.mtu;
-		bufsize = rtnl_tc_calc_bufsize(nl_ticks2us(opts.mtu),
+		bufsize = rtnl_tc_calc_bufsize(tbf->qt_peakrate_txtime,
 					       opts.peakrate.rate);
 		tbf->qt_peakrate_bucket = bufsize;