CI2 Disallowed Key Characters in JSON

In system\core\Input.php.
if( ! preg_match('/^[~a-zA-Z0-9{},:_\/-]+$/i', $str))
{
    exit('Disallowed Key Characters: '.$str);
}
This piece of code triggers Disallowed Key Characters when $str contains:
{"education_level":"1","job_experience":"1","occupation":"41-3011","onet_code"
:"41-3011_00","region":"22220","relevance":"0","school":"0","schoolstate":"0","state":"4","gpa":"0","major"
:"0"}