diff --git a/cpu/cc2538/include/periph_cpu.h b/cpu/cc2538/include/periph_cpu.h
index 2ded24080c27..4e29617b3607 100644
--- a/cpu/cc2538/include/periph_cpu.h
+++ b/cpu/cc2538/include/periph_cpu.h
@@ -153,7 +153,7 @@ typedef enum {
     GPIO_IN_PD      = ((uint8_t)OVERRIDE_PULLDOWN),     /**< input, pull-down */
     GPIO_IN_PU      = ((uint8_t)OVERRIDE_PULLUP),       /**< input, pull-up */
     GPIO_OUT        = ((uint8_t)OVERRIDE_ENABLE),       /**< output */
-    GPIO_OD         = (0xff),                           /**< not supported */
+    GPIO_OD         = (0xfe),                           /**< not supported */
     GPIO_OD_PU      = (0xff)                            /**< not supported */
 } gpio_mode_t;
 /** @} */
diff --git a/cpu/cc2538/periph/gpio.c b/cpu/cc2538/periph/gpio.c
index 82bf84e416e7..4ed0cd709229 100644
--- a/cpu/cc2538/periph/gpio.c
+++ b/cpu/cc2538/periph/gpio.c
@@ -31,7 +31,7 @@
 #define ENABLE_DEBUG 0
 #include "debug.h"
 
-#define MODE_NOTSUP         (0xff)
+#define MODE_NOTSUP         (0xf0)
 
 #ifdef MODULE_PERIPH_GPIO_IRQ
 static gpio_isr_ctx_t isr_ctx[4][8];
@@ -100,7 +100,7 @@ static inline uint8_t _pp_num(gpio_t pin)
 int gpio_init(gpio_t pin, gpio_mode_t mode)
 {
     /* check if mode is valid */
-    if (mode == MODE_NOTSUP) {
+    if (mode >= MODE_NOTSUP) {
         return -1;
     }