cracking salted linux shadow hash: Unable to load due to Line-length

Hi, 

I'm trying to see if I can brute-force a complex pass that is a salted Sha512 using GPU.  The pass is hashed with 8 character salt. 

So when I load the example hashes from hashcat, they load fine, but when I load this one from the shadow file I get line-length exception

hashcat64.exe -a 3 -m 1720 saltedSHA512.txt

hashcat (v3.00-1-g67a8d97) starting...

WARNING: Hashfile 'saltedSHA512.txt' on line 1 <has masked> Line-length exception
Parsed Hashes: 1/1 (100.00%)

ERROR: No hashes loaded

What I have tried so far:
--hex-salt switch
all combinations of 17xx modes

The format of the file:
  Hash: salt
as well as :
  Salt: hash

I'm going nuts, as I cant find any other thread/post anywhere about anyone trying such hash. Im wondering if this is too big for hashcat to handle ?

This hash can be re-generated by python crypt in this format:
crypt(crypt('pass','/$6/$salt/$'))