Assets won't load if base url contains port number

I am running php spark serve to run a codeigniter 4 app locally.

if my $base_url have a port number, all my assets wont load, but it will if i remove the port number

This wont load my assets

Code:

public $baseURL = 'http://localhost:8080/folder_name';

This will load my assets

Code:

public $baseURL = 'http://localhost/folder_name';

Any suggestion as to why and how to fix it?

p.s I already change the base url in .env aswell to http://localhost:8080