diff --git a/lpc111x-isp/lpc111x.c b/lpc111x-isp/lpc111x.c
index c0269c5..5e82852 100644
--- a/lpc111x-isp/lpc111x.c
+++ b/lpc111x-isp/lpc111x.c
@@ -548,7 +548,10 @@ static void start_isp(int power)
 	CLR(TGT_nISP);
 	OUT(TGT_nISP);
 
-	swuart_open(HOST_TX, HOST_RX, BPS);
+	if (swuart_open(HOST_TX, HOST_RX, BPS) < 0) {
+		perror("swuart_open");
+		exit(1);
+	}
 
 	if (!autobaud()) {
 		fprintf(stderr, "target is not responding\n");