diff --git a/src/bts.cpp b/src/bts.cpp
index 9003099a..3ca3628e 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -990,3 +990,17 @@ int gprs_rlcmac_pdch::rcv_block(uint8_t *data, uint8_t len, uint32_t fn, int8_t
 
 	return rc;
 }
+
+struct gprs_rlcmac_tbf *gprs_rlcmac_pdch::ul_tbf_by_tfi(uint8_t tfi)
+{
+	if (tfi >= ARRAY_SIZE(ul_tbf))
+		return NULL;
+	return ul_tbf[tfi];
+}
+
+struct gprs_rlcmac_tbf *gprs_rlcmac_pdch::dl_tbf_by_tfi(uint8_t tfi)
+{
+	if (tfi >= ARRAY_SIZE(dl_tbf))
+		return NULL;
+	return dl_tbf[tfi];
+}
diff --git a/src/bts.h b/src/bts.h
index 128b1e0a..578c63d7 100644
--- a/src/bts.h
+++ b/src/bts.h
@@ -61,6 +61,9 @@ struct gprs_rlcmac_pdch {
 	gprs_rlcmac_bts *bts_data() const;
 	BTS *bts() const;
 	uint8_t trx_no() const;
+
+	struct gprs_rlcmac_tbf *ul_tbf_by_tfi(uint8_t tfi);
+	struct gprs_rlcmac_tbf *dl_tbf_by_tfi(uint8_t tfi);
 #endif
 
 	uint8_t m_is_enabled; /* TS is enabled */
diff --git a/src/gprs_rlcmac_sched.cpp b/src/gprs_rlcmac_sched.cpp
index 123e375f..92e97ece 100644
--- a/src/gprs_rlcmac_sched.cpp
+++ b/src/gprs_rlcmac_sched.cpp
@@ -81,7 +81,7 @@ static uint8_t sched_select_uplink(uint8_t trx, uint8_t ts, uint32_t fn,
 	/* select uplink resource */
 	for (i = 0, tfi = pdch->next_ul_tfi; i < 32;
 	     i++, tfi = (tfi + 1) & 31) {
-		tbf = pdch->ul_tbf[tfi];
+		tbf = pdch->ul_tbf_by_tfi(tfi);
 		/* no TBF for this tfi, go next */
 		if (!tbf)
 			continue;
@@ -169,7 +169,7 @@ static struct msgb *sched_select_downlink(struct gprs_rlcmac_bts *bts,
 	/* select downlink resource */
 	for (i = 0, tfi = pdch->next_dl_tfi; i < 32;
 	     i++, tfi = (tfi + 1) & 31) {
-		tbf = pdch->dl_tbf[tfi];
+		tbf = pdch->dl_tbf_by_tfi(tfi);
 		/* no TBF for this tfi, go next */
 		if (!tbf)
 			continue;