diff --git a/drivers/tty/serial/serial_txx9.c b/drivers/tty/serial/serial_txx9.c
index 7a07e7272de1..7beec331010c 100644
--- a/drivers/tty/serial/serial_txx9.c
+++ b/drivers/tty/serial/serial_txx9.c
@@ -644,6 +644,8 @@ serial_txx9_set_termios(struct uart_port *port, struct ktermios *termios,
 	case CS6:	/* not supported */
 	case CS8:
 		cval |= TXX9_SILCR_UMODE_8BIT;
+		termios->c_cflag &= ~CSIZE;
+		termios->c_cflag |= CS8;
 		break;
 	}