diff --git a/cpu/cc2538/include/periph_cpu.h b/cpu/cc2538/include/periph_cpu.h
index 6ebce4cc6f9726d6daa52fa082100da60403c8b4..05e819065ae44ca1541e3c585acaa57625cabc39 100644
--- a/cpu/cc2538/include/periph_cpu.h
+++ b/cpu/cc2538/include/periph_cpu.h
@@ -60,6 +60,10 @@ typedef uint32_t gpio_t;
  */
 #define GPIO_UNDEF          (0xffffffff)
 
+/**
+ * @brief Custom value to indicate unused parameter in gpio_init_mux
+ */
+#define GPIO_MUX_NONE       (0xff)
 /**
  * @brief   Define a custom GPIO_PIN macro
  *
diff --git a/cpu/cc2538/periph/gpio.c b/cpu/cc2538/periph/gpio.c
index 0dc3f2ef9b7c43f47996cb05a99560a4d9771541..f9196ed0b6e56fd5841e922200f7b9472a9f7dd0 100644
--- a/cpu/cc2538/periph/gpio.c
+++ b/cpu/cc2538/periph/gpio.c
@@ -264,13 +264,13 @@ void gpio_init_mux(gpio_t pin, uint8_t over, uint8_t sel, uint8_t func)
 {
     assert(pin != GPIO_UNDEF);
     /* configure pin function and multiplexing */
-    if (over != MODE_NOTSUP) {
+    if (over != GPIO_MUX_NONE) {
         IOC->OVER[_pp_num(pin)] = over;
     }
-    if (sel != MODE_NOTSUP) {
+    if (sel != GPIO_MUX_NONE) {
         IOC->SEL[_pp_num(pin)] = sel;
     }
-    if (func != MODE_NOTSUP) {
+    if (func != GPIO_MUX_NONE) {
         IOC->PINS[func] = _pp_num(pin);
     }
     /* enable alternative function mode */