diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 40bfd24..77bffd6 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -1153,7 +1153,8 @@
 		var LapdmFrameAB lb := valueof(ts_LAPDm_AB(0, false, false, enc_GsmRrL3Message(meas_rep)));
 		log("LAPDm: ", lb);
 		var octetstring pl := '0000'O & enc_LapdmFrameAB(lb);
-		L1CTL.send(ts_L1CTL_DATA_REQ(g_chan_nr, ts_RslLinkID_SACCH(0), pl));
+		L1CTL.send(ts_L1CTL_DATA_REQ(g_chan_nr, ts_RslLinkID_SACCH(0),
+			f_pad_oct(pl, 23, '2B'O)));
 		repeat;
 		}
 }
@@ -1163,7 +1164,8 @@
 	[] L1CTL.receive(tr_L1CTL_DATA_IND(g_chan_nr, tr_RslLinkID_DCCH(?))) -> value l1_dl {
 		log("DCCH received: ", l1_dl.payload.data_ind.payload);
 		var octetstring pl := '010301'O;
-		L1CTL.send(ts_L1CTL_DATA_REQ(g_chan_nr, ts_RslLinkID_DCCH(0), pl));
+		L1CTL.send(ts_L1CTL_DATA_REQ(g_chan_nr, ts_RslLinkID_DCCH(0),
+			f_pad_oct(pl, 23, '2B'O)));
 		repeat;
 		}
 }
@@ -3222,6 +3224,10 @@
 		/* prepend dummy L1 header */
 		l2 := '0000'O & l2;
 	}
+
+	/* If required, pad L2 frame with constant 0x2b filling */
+	l2 := f_pad_oct(l2, 23, '2B'O);
+
 	log("encoding ", l, " to ", l2);
 	L1CTL.send(ts_L1CTL_DATA_REQ(g_chan_nr, link_id, l2));
 }