diff --git a/drivers/bluetooth/dtl1_cs.c b/drivers/bluetooth/dtl1_cs.c
index 901bdd9..2cc7b32 100644
--- a/drivers/bluetooth/dtl1_cs.c
+++ b/drivers/bluetooth/dtl1_cs.c
@@ -415,6 +415,8 @@
 		hdev->stat.sco_tx++;
 		nsh.type = 0x83;
 		break;
+	default:
+		return -EILSEQ;
 	};
 
 	nsh.zero = 0;