diff --git a/src/host/trxcon/include/osmocom/bb/l1sched/l1sched.h b/src/host/trxcon/include/osmocom/bb/l1sched/l1sched.h
index 3f5e8b045..6c5a31e8e 100644
--- a/src/host/trxcon/include/osmocom/bb/l1sched/l1sched.h
+++ b/src/host/trxcon/include/osmocom/bb/l1sched/l1sched.h
@@ -223,6 +223,8 @@ struct l1sched_lchan_state {
 
 	/*! Queue of Tx primitives */
 	struct llist_head tx_prims;
+	/*! Tx primitive being sent */
+	struct msgb *prim;
 
 	/*! Mode for TCH channels (see GSM48_CMODE_*) */
 	uint8_t	tch_mode;
diff --git a/src/host/trxcon/include/osmocom/bb/trxcon/trxcon_fsm.h b/src/host/trxcon/include/osmocom/bb/trxcon/trxcon_fsm.h
index bbb4eb57d..9eba4fde1 100644
--- a/src/host/trxcon/include/osmocom/bb/trxcon/trxcon_fsm.h
+++ b/src/host/trxcon/include/osmocom/bb/trxcon/trxcon_fsm.h
@@ -105,6 +105,8 @@ struct trxcon_param_tx_data_cnf {
 	uint8_t link_id;
 	uint16_t band_arfcn;
 	uint32_t frame_nr;
+	size_t data_len;
+	const uint8_t *data;
 };
 
 /* param of TRXCON_EV_RX_DATA_IND */
diff --git a/src/host/trxcon/src/sched_lchan_pdtch.c b/src/host/trxcon/src/sched_lchan_pdtch.c
index 4c49504a1..5b884ddc5 100644
--- a/src/host/trxcon/src/sched_lchan_pdtch.c
+++ b/src/host/trxcon/src/sched_lchan_pdtch.c
@@ -160,8 +160,9 @@ int tx_pdtch_fn(struct l1sched_lchan_state *lchan,
 		return -EINVAL;
 	}
 
-	/* Confirm data / traffic sending (pass ownership of the msgb/prim) */
-	l1sched_lchan_emit_data_cnf(lchan, msg, br->fn);
+	/* Cache the prim, so that we can confirm it later (see below) */
+	OSMO_ASSERT(lchan->prim == NULL);
+	lchan->prim = msg;
 
 send_burst:
 	/* Determine which burst should be sent */
@@ -183,5 +184,12 @@ send_burst:
 
 	LOGP_LCHAND(lchan, LOGL_DEBUG, "Scheduled at fn=%u burst=%u\n", br->fn, br->bid);
 
+	if (br->bid == 3) {
+		/* Confirm data / traffic sending (pass ownership of the msgb/prim) */
+		l1sched_lchan_emit_data_cnf(lchan, lchan->prim,
+					    GSM_TDMA_FN_SUB(br->fn, 3));
+		lchan->prim = NULL;
+	}
+
 	return 0;
 }
diff --git a/src/host/trxcon/src/trxcon_fsm.c b/src/host/trxcon/src/trxcon_fsm.c
index f6c9a058f..95458838d 100644
--- a/src/host/trxcon/src/trxcon_fsm.c
+++ b/src/host/trxcon/src/trxcon_fsm.c
@@ -610,6 +610,18 @@ static void trxcon_st_packet_data_action(struct osmo_fsm_inst *fi,
 		l1sched_prim_from_user(trxcon->sched, msg);
 		break;
 	}
+	case TRXCON_EV_TX_DATA_CNF:
+	{
+		const struct trxcon_param_tx_data_cnf *cnf = data;
+		struct msgb *msg;
+
+		msg = l1gprs_handle_ul_block_cnf(trxcon->gprs,
+						 cnf->frame_nr, cnf->chan_nr & 0x07,
+						 cnf->data, cnf->data_len);
+		if (msg != NULL)
+			trxcon_l1ctl_send(trxcon, msg);
+		break;
+	}
 	case TRXCON_EV_RX_DATA_IND:
 	{
 		const struct trxcon_param_rx_data_ind *ind = data;
@@ -655,8 +667,6 @@ static void trxcon_st_packet_data_action(struct osmo_fsm_inst *fi,
 		l1sched_reset(trxcon->sched, false);
 		/* TODO: switch to (not implemented) TRXCON_ST_DCH_TUNING? */
 		break;
-	case TRXCON_EV_TX_DATA_CNF:
-		break;
 	default:
 		OSMO_ASSERT(0);
 	}
diff --git a/src/host/trxcon/src/trxcon_shim.c b/src/host/trxcon/src/trxcon_shim.c
index 54d976a1d..ed2d402e8 100644
--- a/src/host/trxcon/src/trxcon_shim.c
+++ b/src/host/trxcon/src/trxcon_shim.c
@@ -102,6 +102,8 @@ static int handle_prim_data_cnf(struct trxcon_inst *trxcon, struct msgb *msg)
 		.link_id = prim->data_cnf.link_id,
 		.band_arfcn = trxcon->l1p.band_arfcn,
 		.frame_nr = prim->data_cnf.frame_nr,
+		.data_len = msgb_l2len(msg),
+		.data = msgb_l2(msg),
 	};
 
 	if (trxcon->gsmtap != NULL) {