diff --git a/drivers/tty/serial/max3100.c b/drivers/tty/serial/max3100.c
index 475b0a6efce4..17a2ff410305 100644
--- a/drivers/tty/serial/max3100.c
+++ b/drivers/tty/serial/max3100.c
@@ -725,6 +725,7 @@ static int max3100_probe(struct spi_device *spi)
 	max3100s[i]->port.ops = &max3100_ops;
 	max3100s[i]->port.flags = UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
 	max3100s[i]->port.line = i;
+	max3100s[i]->port.iotype = UPIO_BUS;
 	max3100s[i]->port.type = PORT_MAX3100;
 	max3100s[i]->port.dev = &spi->dev;