diff --git a/src/dmm/metex14.c b/src/dmm/metex14.c
index 8151aa9d..5db28cb9 100644
--- a/src/dmm/metex14.c
+++ b/src/dmm/metex14.c
@@ -283,7 +283,7 @@ SR_PRIV int sr_metex14_packet_request(struct sr_serial_dev_inst *serial)
 
 	sr_spew("Requesting DMM packet.");
 
-	return (serial_write(serial, &wbuf, 1) == 1) ? SR_OK : SR_ERR;
+	return (serial_write_nonblocking(serial, &wbuf, 1) == 1) ? SR_OK : SR_ERR;
 }
 #endif
 
diff --git a/src/hardware/serial-dmm/protocol.c b/src/hardware/serial-dmm/protocol.c
index c8127939..e667ca49 100644
--- a/src/hardware/serial-dmm/protocol.c
+++ b/src/hardware/serial-dmm/protocol.c
@@ -110,7 +110,7 @@ static void handle_new_data(struct sr_dev_inst *sdi, int dmm, void *info)
 
 	/* Try to get as much data as the buffer can hold. */
 	len = DMM_BUFSIZE - devc->buflen;
-	len = serial_read(serial, devc->buf + devc->buflen, len);
+	len = serial_read_nonblocking(serial, devc->buf + devc->buflen, len);
 	if (len == 0)
 		return; /* No new bytes, nothing to do. */
 	if (len < 0) {