HTML: What puts in password input when updating

If we are working on a form for create a new user, the password field is empty:

<input type="password" name="password" value="" />

And then, when updating, we would like to show the field filled:

Password: *******

Considering a scenario that passwords are hashed (e.g. with bcrypt), what could we put as value in password input to prefill the field as user's real password?

First, I was thinking about use some "fake" value. The problem of this approach is that passwords length will not be compatible and I will need to check for this every time when user's try to update.