diff --git a/targets/TARGET_NUVOTON/TARGET_M2351/serial_api.c b/targets/TARGET_NUVOTON/TARGET_M2351/serial_api.c
index 348be9572d..d6ad1afdda 100644
--- a/targets/TARGET_NUVOTON/TARGET_M2351/serial_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_M2351/serial_api.c
@@ -250,10 +250,12 @@ void serial_init(serial_t *obj, PinName tx, PinName rx)
     obj->serial.dma_chn_id_rx = DMA_ERROR_OUT_OF_CHANNELS;
 #endif
 
-    // For stdio management
-    if (obj->serial.uart == STDIO_UART) {
+    /* With support for checking H/W UART initialized or not, we allow serial_init(&stdio_uart)
+     * calls in even though H/W UART 'STDIO_UART' has initialized. When serial_init(&stdio_uart)
+     * calls in, we only need to set the 'stdio_uart_inited' flag. */
+    if (((uintptr_t) obj) == ((uintptr_t) &stdio_uart)) {
+        MBED_ASSERT(obj->serial.uart == STDIO_UART);
         stdio_uart_inited = 1;
-        memcpy(&stdio_uart, obj, sizeof(serial_t));
     }
 
     if (var->ref_cnt) {
@@ -302,7 +304,9 @@ void serial_free(serial_t *obj)
         var->obj = NULL;
     }
 
-    if (obj->serial.uart == STDIO_UART) {
+    /* Clear the 'stdio_uart_inited' flag when serial_free(&stdio_uart) calls in. */
+    if (((uintptr_t) obj) == ((uintptr_t) &stdio_uart)) {
+        MBED_ASSERT(obj->serial.uart == STDIO_UART);
         stdio_uart_inited = 0;
     }
 
diff --git a/targets/TARGET_NUVOTON/TARGET_M451/serial_api.c b/targets/TARGET_NUVOTON/TARGET_M451/serial_api.c
index 6c50657ae0..ec557a43e6 100644
--- a/targets/TARGET_NUVOTON/TARGET_M451/serial_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_M451/serial_api.c
@@ -210,12 +210,14 @@ void serial_init(serial_t *obj, PinName tx, PinName rx)
     obj->serial.dma_chn_id_rx = DMA_ERROR_OUT_OF_CHANNELS;
 #endif
 
-    // For stdio management
-    if (obj->serial.uart == STDIO_UART) {
+    /* With support for checking H/W UART initialized or not, we allow serial_init(&stdio_uart)
+     * calls in even though H/W UART 'STDIO_UART' has initialized. When serial_init(&stdio_uart)
+     * calls in, we only need to set the 'stdio_uart_inited' flag. */
+    if (((uintptr_t) obj) == ((uintptr_t) &stdio_uart)) {
+        MBED_ASSERT(obj->serial.uart == STDIO_UART);
         stdio_uart_inited = 1;
-        memcpy(&stdio_uart, obj, sizeof(serial_t));
     }
-    
+
     if (var->ref_cnt) {
         // Mark this module to be inited.
         int i = modinit - uart_modinit_tab;
@@ -256,11 +258,13 @@ void serial_free(serial_t *obj)
     if (var->obj == obj) {
         var->obj = NULL;
     }
-    
-    if (obj->serial.uart == STDIO_UART) {
+
+    /* Clear the 'stdio_uart_inited' flag when serial_free(&stdio_uart) calls in. */
+    if (((uintptr_t) obj) == ((uintptr_t) &stdio_uart)) {
+        MBED_ASSERT(obj->serial.uart == STDIO_UART);
         stdio_uart_inited = 0;
     }
-    
+
     if (! var->ref_cnt) {
         // Mark this module to be deinited.
         int i = modinit - uart_modinit_tab;
diff --git a/targets/TARGET_NUVOTON/TARGET_M480/serial_api.c b/targets/TARGET_NUVOTON/TARGET_M480/serial_api.c
index 8663484f40..356ebcb599 100644
--- a/targets/TARGET_NUVOTON/TARGET_M480/serial_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_M480/serial_api.c
@@ -240,10 +240,12 @@ void serial_init(serial_t *obj, PinName tx, PinName rx)
     obj->serial.dma_chn_id_rx = DMA_ERROR_OUT_OF_CHANNELS;
 #endif
 
-    // For stdio management
-    if (obj->serial.uart == STDIO_UART) {
+    /* With support for checking H/W UART initialized or not, we allow serial_init(&stdio_uart)
+     * calls in even though H/W UART 'STDIO_UART' has initialized. When serial_init(&stdio_uart)
+     * calls in, we only need to set the 'stdio_uart_inited' flag. */
+    if (((uintptr_t) obj) == ((uintptr_t) &stdio_uart)) {
+        MBED_ASSERT(obj->serial.uart == STDIO_UART);
         stdio_uart_inited = 1;
-        memcpy(&stdio_uart, obj, sizeof(serial_t));
     }
 
     if (var->ref_cnt) {
@@ -289,7 +291,9 @@ void serial_free(serial_t *obj)
         var->obj = NULL;
     }
 
-    if (obj->serial.uart == STDIO_UART) {
+    /* Clear the 'stdio_uart_inited' flag when serial_free(&stdio_uart) calls in. */
+    if (((uintptr_t) obj) == ((uintptr_t) &stdio_uart)) {
+        MBED_ASSERT(obj->serial.uart == STDIO_UART);
         stdio_uart_inited = 0;
     }
 
diff --git a/targets/TARGET_NUVOTON/TARGET_NANO100/serial_api.c b/targets/TARGET_NUVOTON/TARGET_NANO100/serial_api.c
index 1fb741e15e..447d8fb5d8 100644
--- a/targets/TARGET_NUVOTON/TARGET_NANO100/serial_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_NANO100/serial_api.c
@@ -175,12 +175,14 @@ void serial_init(serial_t *obj, PinName tx, PinName rx)
     obj->serial.dma_chn_id_rx = DMA_ERROR_OUT_OF_CHANNELS;
 #endif
 
-    // For stdio management
-    if (obj->serial.uart == STDIO_UART) {
+    /* With support for checking H/W UART initialized or not, we allow serial_init(&stdio_uart)
+     * calls in even though H/W UART 'STDIO_UART' has initialized. When serial_init(&stdio_uart)
+     * calls in, we only need to set the 'stdio_uart_inited' flag. */
+    if (((uintptr_t) obj) == ((uintptr_t) &stdio_uart)) {
+        MBED_ASSERT(obj->serial.uart == STDIO_UART);
         stdio_uart_inited = 1;
-        memcpy(&stdio_uart, obj, sizeof(serial_t));
     }
-    
+
     if (var->ref_cnt) {
         // Mark this module to be inited.
         int i = modinit - uart_modinit_tab;
@@ -221,11 +223,13 @@ void serial_free(serial_t *obj)
     if (var->obj == obj) {
         var->obj = NULL;
     }
-    
-    if (obj->serial.uart == STDIO_UART) {
+
+    /* Clear the 'stdio_uart_inited' flag when serial_free(&stdio_uart) calls in. */
+    if (((uintptr_t) obj) == ((uintptr_t) &stdio_uart)) {
+        MBED_ASSERT(obj->serial.uart == STDIO_UART);
         stdio_uart_inited = 0;
     }
-    
+
     if (! var->ref_cnt) {
         // Mark this module to be deinited.
         int i = modinit - uart_modinit_tab;
diff --git a/targets/TARGET_NUVOTON/TARGET_NUC472/serial_api.c b/targets/TARGET_NUVOTON/TARGET_NUC472/serial_api.c
index eeeca799ae..002f23ef48 100644
--- a/targets/TARGET_NUVOTON/TARGET_NUC472/serial_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_NUC472/serial_api.c
@@ -240,12 +240,14 @@ void serial_init(serial_t *obj, PinName tx, PinName rx)
     obj->serial.dma_chn_id_rx = DMA_ERROR_OUT_OF_CHANNELS;
 #endif
 
-    // For stdio management
-    if (obj->serial.uart == STDIO_UART) {
+    /* With support for checking H/W UART initialized or not, we allow serial_init(&stdio_uart)
+     * calls in even though H/W UART 'STDIO_UART' has initialized. When serial_init(&stdio_uart)
+     * calls in, we only need to set the 'stdio_uart_inited' flag. */
+    if (((uintptr_t) obj) == ((uintptr_t) &stdio_uart)) {
+        MBED_ASSERT(obj->serial.uart == STDIO_UART);
         stdio_uart_inited = 1;
-        memcpy(&stdio_uart, obj, sizeof(serial_t));
     }
-    
+
     if (var->ref_cnt) {
         // Mark this module to be inited.
         int i = modinit - uart_modinit_tab;
@@ -286,11 +288,13 @@ void serial_free(serial_t *obj)
     if (var->obj == obj) {
         var->obj = NULL;
     }
-    
-    if (obj->serial.uart == STDIO_UART) {
+
+    /* Clear the 'stdio_uart_inited' flag when serial_free(&stdio_uart) calls in. */
+    if (((uintptr_t) obj) == ((uintptr_t) &stdio_uart)) {
+        MBED_ASSERT(obj->serial.uart == STDIO_UART);
         stdio_uart_inited = 0;
     }
-    
+
     if (! var->ref_cnt) {
         // Mark this module to be deinited.
         int i = modinit - uart_modinit_tab;