diff --git a/firmware/ec/test/fake/fake_GPIO.c b/firmware/ec/test/fake/fake_GPIO.c
index 7175d1282c..03d309e690 100644
--- a/firmware/ec/test/fake/fake_GPIO.c
+++ b/firmware/ec/test/fake/fake_GPIO.c
@@ -65,6 +65,10 @@ static int FakeGpio_setCallback(const OcGpio_Pin *pin,
         return OCGPIO_FAILURE;
     }
 
+    if (pin->idx >= FAKE_GPIO_PIN_COUNT) {
+        return OCGPIO_FAILURE;
+    } 
+
     obj->callback[pin->idx].fn = callback;
     obj->callback[pin->idx].context = context;
     return OCGPIO_SUCCESS;