Missing parantheses compiler warning

[Dead2]

crc_folding.c: In function ‘crc_fold_copy’:
crc_folding.c:288:19: warning: suggest parentheses around ‘-’ in operand of ‘&’ [-Wparentheses]
algn_diff = 0 - (unsigned long)src & 0xF;

I am unsure what the correct behaviour is here, and hope that someone who knows the algorithm can clarify this in the code.