diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index ea75937..0b8decd 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -3769,6 +3769,31 @@
 	}
 }
 
+/* Send I-frame from MS and expect it to arrive as RLL DATA IND on Abis */
+private function f_data_mo(
+	RslLinkId link_id,
+	boolean p, uint3_t nr, uint3_t ns,
+	octetstring l3,
+	boolean exp_sacch := true, /* Should tolerate SACCH messages? */
+	boolean exp_any := true /* Should tolerate any other RSL messages? */
+) runs on ConnHdlr {
+	timer T := 3.0;
+	f_tx_lapdm(ts_LAPDm_I(link_id.sapi, cr_MO_CMD, p, nr, ns, l3), link_id);
+	T.start;
+	/* Expect RLL DATA IND on RSL side */
+	alt {
+	[] RSL.receive(tr_RSL_DATA_IND(g_chan_nr, link_id, l3)) {
+		setverdict(pass);
+		}
+	[] as_rsl_sacch_ind(exp_sacch);
+	[] as_rsl_any_ind(exp_any);
+	[] T.timeout {
+		setverdict(fail, "Timeout waiting for DATA_IND");
+		mtc.stop;
+		}
+	}
+}
+
 /* Test channel activation with A5/n right from the beginning (like in assignment + hand-over) */
 function f_TC_chan_act_encr(charstring id) runs on ConnHdlr {
 	f_l1_tune(L1CTL);
@@ -3832,10 +3857,8 @@
 	var uint8_t alg_id := f_alg_id_to_l1ctl(g_pars.encr.alg_id);
 	f_L1CTL_CRYPTO_REQ(L1CTL, g_pars.chan_nr, alg_id, g_pars.encr.key);
 
-	/* send first ciphered I-frame in response */
-	l3 := '0a0b0c0d'O;
-	f_tx_lapdm(ts_LAPDm_I(link_id.sapi, cr_MO_CMD, true, 1, 0, l3), link_id);
-	RSL.receive(tr_RSL_DATA_IND(g_chan_nr, link_id, l3));
+	/* send first ciphered I-frame in response and expect it on RSL */
+	f_data_mo(link_id, true, 1, 0, '0a0b0c0d'O, exp_sacch := true);
 
 	/* now the BTS code should have detected the first properly encrypted uplink I-frame,
 	 * and hence enable encryption also on the downlink */