diff --git a/drivers/tty/serial/serial_txx9.c b/drivers/tty/serial/serial_txx9.c
index 29f5232f79e4..af115645c51f 100644
--- a/drivers/tty/serial/serial_txx9.c
+++ b/drivers/tty/serial/serial_txx9.c
@@ -142,7 +142,6 @@ struct uart_txx9_port {
 #define TXX9_SIFCR_RDIL_12	0x00000180
 #define TXX9_SIFCR_RDIL_MAX	0x00000180
 #define TXX9_SIFCR_TDIL_MASK	0x00000018
-#define TXX9_SIFCR_TDIL_MASK	0x00000018
 #define TXX9_SIFCR_TDIL_1	0x00000000
 #define TXX9_SIFCR_TDIL_4	0x00000001
 #define TXX9_SIFCR_TDIL_8	0x00000010