diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index d667344..82a83cf 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -8815,10 +8815,11 @@
 	if (g_pars.fhp.enabled) {
 		ch_desc := valueof(ts_ChanDescH1(g_pars.chan_nr, g_pars.fhp.maio_hsn, g_pars.tsc));
 	} else {
-		ch_desc := valueof(ts_ChanDescH0(g_pars.chan_nr, mp_trx_pars[0].arfcn, g_pars.tsc));
+		var GsmArfcn arfcn := mp_trx_pars[g_pars.trx_nr].arfcn;
+		ch_desc := valueof(ts_ChanDescH0(g_pars.chan_nr, arfcn, g_pars.tsc));
 	}
 	var GsmRrMessage rr_msg := valueof(ts_IMM_ASS(ra, fn, 0, ch_desc, g_pars.fhp.ma_map));
-	RSL.send(ts_RSL_IMM_ASSIGN(enc_GsmRrMessage(rr_msg)));
+	RSL.send(ts_ASP_RSL_UD(ts_RSL_IMM_ASSIGN(enc_GsmRrMessage(rr_msg)))); /* force sending to TRX0 */
 
 	/* Do not expect the Immediate Assignment to show up on MS side yet. Even give it one second before the BSC
 	 * requests Chan Activ, to make sure the RR IMM ASS is held back. */
@@ -8859,10 +8860,20 @@
 
 testcase TC_early_immediate_assignment() runs on test_CT {
 	var ConnHdlr vc_conn;
-	var ConnHdlrPars pars := valueof(t_Pars(t_RslChanNr_Bm(1), ts_RSL_ChanMode_SIGN));
+	var ConnHdlrPars pars;
+
 	f_init();
+
+	/* verify early Immediate Assignment on C0 (the BCCH carrier): TCH/F on TS1 */
+	pars := valueof(t_Pars(t_RslChanNr_Bm(1), ts_RSL_ChanMode_SIGN, trx_nr := 0));
 	vc_conn := f_start_handler(refers(f_TC_early_immediate_assignment), pars);
 	vc_conn.done;
+
+	/* verify early Immediate Assignment on C1: TCH/F on TS0 */
+	pars := valueof(t_Pars(t_RslChanNr_Bm(0), ts_RSL_ChanMode_SIGN, trx_nr := 1));
+	vc_conn := f_start_handler(refers(f_TC_early_immediate_assignment), pars);
+	vc_conn.done;
+
 	Misc_Helpers.f_shutdown(__BFILE__, __LINE__);
 }