diff --git a/kernel/drivers/spi/spi-master.c b/kernel/drivers/spi/spi-master.c
index 104af8023f3ac855d0d7d84cc23e7e0add55c949..0fad328ef7dd0d34591c40ff83ecd04d18da2f69 100644
--- a/kernel/drivers/spi/spi-master.c
+++ b/kernel/drivers/spi/spi-master.c
@@ -181,7 +181,7 @@ static int spi_master_ioctl_rt(struct rtdm_fd *fd,
 	case SPI_RTIOC_TRANSFER_N:
 		ret = -EINVAL;
 		if (master->ops->transfer_iobufs_n) {
-			len = (int)arg;
+			len = (long)arg;
 			rtdm_mutex_lock(&master->bus_lock);
 			ret = do_chip_select(slave);
 			if (ret == 0) {