PVS-Studio warning V610 for usrsctp

void
sctp_send_sack(struct sctp_tcb *stcb, int so_locked)
{
  ....
  tsn_map &= (~0 << (1 - offset));
  ....
}

This suspicious code was found in usrsctp project by PVS-Studio static code analyzer.
Warning message is:
V610 Undefined behavior. Check the shift operator '<<. The left operand '~0' is negative. sctp_output.c 10898

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/