My error message says "Oops, try again. Your function fails on digit_sum(434). It returns None when it should return 11." But when I print digit_sum(434) it does print 11, and any other number I test works too. I can't figure out what I've left out or if this is possibly a glitch of some sort. Any help is much appreciated.

```
numsum=[]
def digit_sum(n):
add_up=str(n)
for n in add_up[0: len(add_up)+1]:
numsum.append(int(n))
sumsum=sum(numsum)
print sumsum
digit_sum(434)
```