check_signed.c false negative

Given:

enum ib_qp_state {
        IB_QPS_RESET,
        IB_QPS_INIT,
        IB_QPS_RTR,
        IB_QPS_RTS,
        IB_QPS_SQD,
        IB_QPS_SQE,
        IB_QPS_ERR
};

int p(enum ib_qp_state cur_state, enum ib_qp_state next_state)
{
#if 0
       if (cur_state  < 0 || cur_state > IB_QPS_ERR ||
         next_state < 0 || next_state > IB_QPS_ERR) {
                return (5);
        }
#else
       if (next_state < 0 || next_state > IB_QPS_ERR) {
                return (5);
        }
#endif

        return (0);
}

current smatch is happy. But "#if 1" above instead, and:

jlevon@sent:~/src/smatch$ ./smatch a.c
./smatch: a.c:15 p() warn: unsigned 'cur_state' is never less than zero.

Why is "next_state" not reported equally?

thanks
john