diff --git a/cpu/atmega2560/periph/gpio.c b/cpu/atmega2560/periph/gpio.c
index 610fa9936efc642e4b577cb64f71acf409340494..36921d30fc819f496e4cb317757d999a562a0225 100644
--- a/cpu/atmega2560/periph/gpio.c
+++ b/cpu/atmega2560/periph/gpio.c
@@ -32,7 +32,7 @@
 #define GPIO_OFFSET_PORT_H      (0xCB)
 #define GPIO_OFFSET_PIN_PORT    (0x02)
 #define GPIO_OFFSET_PIN_PIN     (0x03)
-#define GPIO_EXT_INT_NUMOF      (7U)
+#define GPIO_EXT_INT_NUMOF      (8U)
 
 typedef struct {
     gpio_cb_t cb;