I was looking at this solution:

```
#Write your function here
def double_index(lst, index):
if index < len(lst):
lst[index] = lst[index] * 2
return lst
#Uncomment the line below when your function is done
print(double_index([3, 8, 9, 12], -7))
```

i think IF statement is not correct validation. I can write negative numbers in the len of list. In this case -4. But if i put in index -5 i get error. It is smaller than len(lst) but it is not valid index.