Parse error: syntax error in system/core/Security.php on line 620

Hi, I keep hitting this error on my production server.

Code:

Parse error: syntax error, unexpected '?' system/core/Security.php on line 620

My local testing machine running mamp does not produce this error.

Does anyone know what the problem could be?

I am running CI RC3 and I checked my Online ./CodeIgniter-3-0rc3/system/core/Security.php

and this was the line 620:

* @param string $charset Character set

I think you should first check to ensure you have the correct file version and also upload your local Security.php