diff --git a/bsc/MSC_ConnectionHandler.ttcn b/bsc/MSC_ConnectionHandler.ttcn
index 6bf3221..44def3b 100644
--- a/bsc/MSC_ConnectionHandler.ttcn
+++ b/bsc/MSC_ConnectionHandler.ttcn
@@ -477,20 +477,19 @@
 /* Convert from Ericsson ChanDesc2 format to Osmocom RslChannelNr format */
 function f_ChDesc2RslChanNr(ChannelDescription2_V ch_desc, out RslChannelNr chan_nr, out GsmArfcn arfcn) {
 	var BIT5 inp := ch_desc.channelTypeandTDMAOffset;
-
-	chan_nr.tn := bit2int(ch_desc.timeslotNumber);
+	var uint3_t tn := bit2int(ch_desc.timeslotNumber);
 
 	if (match(inp, '00001'B)) { /* TCH/F */
-		chan_nr.u.ch0 := RSL_CHAN_NR_Bm_ACCH;
+		chan_nr := valueof(t_RslChanNr_Bm(tn));
 	}
 	else if (match(inp, '0001?'B)) { /* TCH/H */
-		chan_nr.u.lm.sub_chan := bit2int(substr(inp, 4, 1));
+		chan_nr := valueof(t_RslChanNr_Lm(tn, bit2int(substr(inp, 4, 1))));
 	}
 	else if (match(inp, '001??'B)) { /* SDCCH/4 */
-		chan_nr.u.sdcch4.sub_chan := bit2int(substr(inp, 3, 2));
+		chan_nr := valueof(t_RslChanNr_SDCCH4(tn, bit2int(substr(inp, 3, 2))));
 	}
 	else if (match(inp, '01???'B)) { /* SDCCH/8 */
-		chan_nr.u.sdcch8.sub_chan := bit2int(substr(inp, 2, 3));
+		chan_nr := valueof(t_RslChanNr_SDCCH8(tn, bit2int(substr(inp, 2, 3))));
 	}
 	else {
 		setverdict(fail, "Unknown ChDesc!");