diff --git a/tests/bluetooth/tester/src/bttester.c b/tests/bluetooth/tester/src/bttester.c
index b72fbbdfaf4..4e4022920d5 100644
--- a/tests/bluetooth/tester/src/bttester.c
+++ b/tests/bluetooth/tester/src/bttester.c
@@ -104,6 +104,7 @@ static void register_service(u8_t *data, u16_t len)
 		break;
 #endif /* CONFIG_BT_MESH */
 	default:
+		LOG_WRN("unknown id: 0x%02x", cmd->id);
 		status = BTP_STATUS_FAILED;
 		break;
 	}
@@ -136,6 +137,7 @@ static void unregister_service(u8_t *data, u16_t len)
 		break;
 #endif /* CONFIG_BT_MESH */
 	default:
+		LOG_WRN("unknown id: 0x%x", cmd->id);
 		status = BTP_STATUS_FAILED;
 		break;
 	}
@@ -148,6 +150,7 @@ static void handle_core(u8_t opcode, u8_t index, u8_t *data,
 			u16_t len)
 {
 	if (index != BTP_INDEX_NONE) {
+		LOG_WRN("index != BTP_INDEX_NONE: 0x%x", index);
 		tester_rsp(BTP_SERVICE_ID_CORE, opcode, index, BTP_STATUS_FAILED);
 		return;
 	}
@@ -166,6 +169,7 @@ static void handle_core(u8_t opcode, u8_t index, u8_t *data,
 		unregister_service(data, len);
 		return;
 	default:
+		LOG_WRN("unknown opcode: 0x%x", opcode);
 		tester_rsp(BTP_SERVICE_ID_CORE, opcode, BTP_INDEX_NONE,
 			   BTP_STATUS_UNKNOWN_CMD);
 		return;
@@ -212,6 +216,7 @@ static void cmd_handler(void *p1, void *p2, void *p3)
 			break;
 #endif /* CONFIG_BT_MESH */
 		default:
+			LOG_WRN("unknown service: 0x%x", cmd->hdr.service);
 			tester_rsp(cmd->hdr.service, cmd->hdr.opcode,
 				   cmd->hdr.index, BTP_STATUS_FAILED);
 			break;