```
digits = []
def digit_sum(n):
for x in str(n):
digits.append(int(x))
print sum(digits)
```

Python tells me that my function returns none. However, when I run the function myself it returns the correct answer. I feel like I'm going crazy!

"Oops, try again. Your function fails on digit_sum(434). It returns None when it should return 11"