diff --git a/src/osmo-bts-sysmo/l1_if.c b/src/osmo-bts-sysmo/l1_if.c
index 247c37128..f682ffdd8 100644
--- a/src/osmo-bts-sysmo/l1_if.c
+++ b/src/osmo-bts-sysmo/l1_if.c
@@ -386,7 +386,7 @@ static int ph_data_req(struct gsm_bts_trx *trx, struct msgb *msg,
 		/* The sapi depends on DSP configuration, not
 		 * on the actual SYSTEM INFORMATION 3. */
 		u8BlockNbr = l1sap_fn2ccch_block(u32Fn);
-		if (u8BlockNbr >= 1)
+		if (u8BlockNbr >= num_agch(trx, "PH-DATA-REQ"))
 			sapi = GsmL1_Sapi_Pch;
 		else
 			sapi = GsmL1_Sapi_Agch;
diff --git a/src/osmo-bts-virtual/scheduler_virtbts.c b/src/osmo-bts-virtual/scheduler_virtbts.c
index 997ccbc25..2248afc54 100644
--- a/src/osmo-bts-virtual/scheduler_virtbts.c
+++ b/src/osmo-bts-virtual/scheduler_virtbts.c
@@ -79,7 +79,8 @@ static void tx_to_virt_um(struct l1sched_trx *l1t, uint8_t tn, uint32_t fn,
 	timeslot = tn;
 	/* in Osmocom, AGCH is only sent on ccch block 0. no idea why. this seems to cause false GSMTAP channel
 	 * types for agch and pch. */
-	if (rsl_chantype == RSL_CHAN_PCH_AGCH && l1sap_fn2ccch_block(fn) == 0)
+	if (rsl_chantype == RSL_CHAN_PCH_AGCH &&
+	    l1sap_fn2ccch_block(fn) >= num_agch(l1t->trx, "PH-DATA-REQ"))
 		gsmtap_chantype = GSMTAP_CHANNEL_PCH;
 	else
 		gsmtap_chantype = chantype_rsl2gsmtap(rsl_chantype, chdesc->link_id); /* the logical channel type */