diff --git a/src/bts.cpp b/src/bts.cpp
index 06ac5a7..cf39aa4 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -632,7 +632,7 @@
 	unsigned int best_cnt = 0;
 	uint8_t best_first_tfi = 0;
 
-	if (use_trx >= 0 && use_trx < 8)
+	if (use_trx >= 0 && use_trx < (int8_t)ARRAY_SIZE(bts->trx))
 		trx_from = trx_to = use_trx;
 	else {
 		trx_from = 0;