PVS-Studio warning V584 for Asterisk

static void check_send_queue(struct unistimsession *pte)
{
  if (pte->last_buf_available == 1) {
    ....
  }
  else if (pte->last_seq_ack + 1 == pte->seq_server + 1) {  //<==
    ....
  }
}

This suspicious code was found in Asterisk project by PVS-Studio static code analyzer.
Warning message is:
V584 The '1' value is present on both sides of the '==' operator. The expression is incorrect or it can be simplified. chan_unistim.c 1095

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