diff --git a/targets/TARGET_NUVOTON/TARGET_M451/watchdog_api.c b/targets/TARGET_NUVOTON/TARGET_M451/watchdog_api.c
index 1ac841e78e..38bd1b44b5 100644
--- a/targets/TARGET_NUVOTON/TARGET_M451/watchdog_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_M451/watchdog_api.c
@@ -23,7 +23,7 @@
 
 /* Define WDT clock source in target configuration option */
 #ifndef MBED_CONF_TARGET_WDT_CLKSRC_SEL
-#define MBED_CONF_TARGET_WDT_CLKSRC_SEL     LIRC
+#define MBED_CONF_TARGET_WDT_CLKSRC_SEL     LXT
 #endif
 
 /* WDT clock source definition */
diff --git a/targets/TARGET_NUVOTON/TARGET_M480/watchdog_api.c b/targets/TARGET_NUVOTON/TARGET_M480/watchdog_api.c
index 1f42b89898..55af188e5b 100644
--- a/targets/TARGET_NUVOTON/TARGET_M480/watchdog_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_M480/watchdog_api.c
@@ -24,7 +24,7 @@
 
 /* Define WDT clock source in target configuration option */
 #ifndef MBED_CONF_TARGET_WDT_CLKSRC_SEL
-#define MBED_CONF_TARGET_WDT_CLKSRC_SEL     LIRC
+#define MBED_CONF_TARGET_WDT_CLKSRC_SEL     LXT
 #endif
 
 /* WDT clock source definition */
diff --git a/targets/TARGET_NUVOTON/TARGET_NUC472/watchdog_api.c b/targets/TARGET_NUVOTON/TARGET_NUC472/watchdog_api.c
index 9480a6ce79..ca2ada2868 100644
--- a/targets/TARGET_NUVOTON/TARGET_NUC472/watchdog_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_NUC472/watchdog_api.c
@@ -22,7 +22,7 @@
 
 /* Define WDT clock source in target configuration option */
 #ifndef MBED_CONF_TARGET_WDT_CLKSRC_SEL
-#define MBED_CONF_TARGET_WDT_CLKSRC_SEL     LIRC
+#define MBED_CONF_TARGET_WDT_CLKSRC_SEL     LXT
 #endif
 
 /* WDT clock source definition */