Bug in autovacuum.c?

Looking over the autovacuum.c code, I see:

    /*
     * Determine the oldest datfrozenxid/relfrozenxid that we will allow to
     * pass without forcing a vacuum.  (This limit can be tightened for
     * particular tables, but not loosened.)
     */
    recentXid = ReadNewTransactionId();
    xidForceLimit = recentXid - autovacuum_freeze_max_age;
    /* ensure it's a "normal" XID, else TransactionIdPrecedes misbehaves */
    if (xidForceLimit < FirstNormalTransactionId)
        xidForceLimit -= FirstNormalTransactionId;

This last line doesn't look right to me;  should it be:

        xidForceLimit = FirstNormalTransactionId;

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +