diff --git a/openbsc/src/trau_mux.c b/openbsc/src/trau_mux.c
index 477ea21..9930751 100644
--- a/openbsc/src/trau_mux.c
+++ b/openbsc/src/trau_mux.c
@@ -185,7 +185,7 @@
 			return -EINVAL;
 		if (!ue->callref)
 			return -EINVAL;
-		if (memcpy(tf.c_bits, c_bits_check, sizeof(c_bits_check)))
+		if (memcmp(tf.c_bits, c_bits_check, sizeof(c_bits_check)))
 			DEBUGPC(DMUX, "illegal trau (C1-C5) %s\n",
 				hexdump(tf.c_bits, sizeof(c_bits_check)));
 		msg = msgb_alloc(sizeof(struct gsm_data_frame) + 33,