diff --git a/src/osmo-bts-sysmo/sysmo_l1_if.c b/src/osmo-bts-sysmo/sysmo_l1_if.c
index c7c54dd9..c072c1a6 100644
--- a/src/osmo-bts-sysmo/sysmo_l1_if.c
+++ b/src/osmo-bts-sysmo/sysmo_l1_if.c
@@ -155,7 +155,7 @@ static int handle_ph_readytosend_ind(struct femtol1_hdl *fl1h,
 	switch (rts_ind->sapi) {
 	case GsmL1_Sapi_Pdtch:
 	case GsmL1_Sapi_Pacch:
-		rc = pcu_rx_rts_req_pdtch((long)fl1h->priv, rts_ind->u8Tn,
+		rc = pcu_rx_rts_req_pdtch(fl1h->trx_no, rts_ind->u8Tn,
 			rts_ind->u16Arfcn, rts_ind->u32Fn, rts_ind->u8BlockNbr);
 	case GsmL1_Sapi_Ptcch:
 		// FIXME
@@ -215,7 +215,7 @@ static int handle_ph_data_ind(struct femtol1_hdl *fl1h,
 			!= GsmL1_PdtchPlType_Full)
 			break;
 		/* PDTCH / PACCH frame handling */
-		pcu_rx_data_ind_pdtch((long)fl1h->priv, data_ind->u8Tn,
+		pcu_rx_data_ind_pdtch(fl1h->trx_no, data_ind->u8Tn,
 			data_ind->msgUnitParam.u8Buffer + 1,
 			data_ind->msgUnitParam.u8Size - 1,
 			data_ind->u32Fn,
@@ -357,7 +357,7 @@ int l1if_pdch_req(void *obj, uint8_t ts, int is_ptcch, uint32_t fn,
 	return 0;
 }
 
-void *l1if_open_pdch(void *priv, uint32_t hlayer1, struct gsmtap_inst *gsmtap)
+void *l1if_open_pdch(uint8_t trx_no, uint32_t hlayer1, struct gsmtap_inst *gsmtap)
 {
 	struct femtol1_hdl *fl1h;
 	int rc;
@@ -367,7 +367,7 @@ void *l1if_open_pdch(void *priv, uint32_t hlayer1, struct gsmtap_inst *gsmtap)
 		return NULL;
 
 	fl1h->hLayer1 = hlayer1;
-	fl1h->priv = priv;
+	fl1h->trx_no = trx_no;
 	fl1h->clk_cal = 0;
 	/* default clock source: OCXO */
 	fl1h->clk_src = SuperFemto_ClkSrcId_Ocxo;
diff --git a/src/osmo-bts-sysmo/sysmo_l1_if.h b/src/osmo-bts-sysmo/sysmo_l1_if.h
index 6b50d4e3..8f1857e4 100644
--- a/src/osmo-bts-sysmo/sysmo_l1_if.h
+++ b/src/osmo-bts-sysmo/sysmo_l1_if.h
@@ -38,7 +38,7 @@ struct femtol1_hdl {
 	struct gsmtap_inst *gsmtap;
 	uint32_t gsmtap_sapi_mask;
 
-	void *priv;			/* user reference */
+	uint8_t trx_no;
 
 	struct osmo_timer_list alive_timer;
 	unsigned int alive_prim_cnt;
diff --git a/src/pcu_l1_if.cpp b/src/pcu_l1_if.cpp
index 67272ab0..790789c8 100644
--- a/src/pcu_l1_if.cpp
+++ b/src/pcu_l1_if.cpp
@@ -44,7 +44,8 @@ extern "C" {
 
 // FIXME: move this, when changed from c++ to c.
 extern "C" {
-void *l1if_open_pdch(void *priv, uint32_t hlayer1, struct gsmtap_inst *gsmtap);
+void *l1if_open_pdch(uint8_t trx_no, uint32_t hlayer1,
+		     struct gsmtap_inst *gsmtap);
 int l1if_connect_pdch(void *obj, uint8_t ts);
 int l1if_pdch_req(void *obj, uint8_t ts, int is_ptcch, uint32_t fn,
         uint16_t arfcn, uint8_t block_nr, uint8_t *data, uint8_t len);
@@ -330,8 +331,8 @@ static int pcu_rx_info_ind(struct gsm_pcu_if_info_ind *info_ind)
 	struct gprs_bssgp_pcu *pcu;
 	struct gprs_rlcmac_pdch *pdch;
 	struct in_addr ia;
-	int rc = 0;
-	int trx, ts;
+	int rc = 0, ts;
+	uint8_t trx;
 	int i;
 
 	if (info_ind->version != PCU_IF_VERSION) {
@@ -450,7 +451,7 @@ bssgp_failed:
 				info_ind->trx[trx].hlayer1);
 				if (!bts->trx[trx].fl1h)
 					bts->trx[trx].fl1h = l1if_open_pdch(
-						(void *)trx,
+						trx,
 						info_ind->trx[trx].hlayer1,
 						bts->gsmtap);
 			if (!bts->trx[trx].fl1h) {