How to set Int64 as constant?

1

I want to set default value in function nextTime, at example:

  public function nextTime(prevTime:Int64 = DEFAULT_TIMESTAMP):Int64
  { .... }

where DEFAULT_TIMESTAMP should be 1577836800000

 public static inline var  DEFAULT_TIMESTAMP = Int64.make(0x0000016F,0x5E66E800);

In Haxe it’s not possible to have a constant from Int64 type , but default value for nextTime require constant . Float is not a solution because have bitwise operation with prevTime and I don’t want to do always Int64.fromFloat

How can I get around the problem?

2 
function nextTime(?prevTime:Int64):Int64 {
  if(prevTime == null)
    prevTime = defaultTimestamp;
  //...
}
3

Thank you ! Based on your solution that will work too

function nextTime(prevTime:Null<Int64>=null):Int64 {
  if(prevTime == null)
    prevTime = defaultTimestamp;
  //...
}