XOR in PHQL

I keep getting this Error when using XOR in PHQL. Is it not supported or am I doing something wrong?

... Uncaught exception 'Phalcon\Mvc\Model\Exception' with message 'Syntax error, unexpected token IDENTIFIER(XOR), near to ...

If you can provide us with your code, maybe that would be helpful. It's not much I can help you here, if all your giving us is the error message.