Extending theme with hyphen on folder name

Is there a problem with themes that use hyphen on their folder name? I'm trying to extend gravstrap-theme, and getting:

Whoops \ Exception \ ErrorException (E_PARSE)
syntax error, unexpected '-', expecting '{'

My code:

<?php
   namespace Grav\Theme;
   use Grav\Common\Theme;
   class MyThemeName extends Gravstrap-Theme
{
}
---

Gravstrap-Theme is not a compatible class name. Php does not allow hyphens in the class name. Presuming you have the Gravstrap theme installed your class would look more like class MyThemeName extends GravstrapTheme (without a hyphen)

What he said :)