Extending CI_Exceptions is not working?

[eluser]Unknown[/eluser]
Hi, I want to override the show_404 function in the CI_Exceptions.
It's working in my 2 local servers(Apache) but it's not working in my live server(LiteSpeed).

Is this Codeigniter bug or LiteSpeed restrictions?
Other classes and models that I've extended are working, it's just the CI_Exceptions doesn't work..

However, If I replace the core class entirely, it works.