diff --git a/targets/TARGET_NUVOTON/TARGET_M2351/gpio_api.c b/targets/TARGET_NUVOTON/TARGET_M2351/gpio_api.c
index 5197234eaa..84e77e5fca 100644
--- a/targets/TARGET_NUVOTON/TARGET_M2351/gpio_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_M2351/gpio_api.c
@@ -37,6 +37,11 @@ uint32_t gpio_set(PinName pin)
     return (uint32_t)(1 << pin_index);    // Return the pin mask
 }
 
+int gpio_is_connected(const gpio_t *obj)
+{
+    return (obj->pin != (PinName) NC);
+}
+
 void gpio_init(gpio_t *obj, PinName pin)
 {
     obj->pin = pin;
@@ -86,4 +91,4 @@ void gpio_dir(gpio_t *obj, PinDirection direction)
     
     GPIO_SetMode(gpio_base, 1 << pin_index, mode_intern);
 }
-#endif
\ No newline at end of file
+#endif