Extend Laravel's Blade: not able to add an extension

I've registered a Blade extension in my Laravel (5.0) project:

Blade::extend(function($view, $compiler)
{
    // my extension code
);

But the function is never fired and the extension is not working (the ServiceProvider I'm using to register the extension is fired though). I've tried to put the code in my routes.php file but that doesn't do anything either. I've also checked the BladeCompiler class in the library, and the 'compileExtensions' method never gets fired (and that seems to be where the custom extensions are registered).

Am I doing something wrong? Do I have to register somewhere that I want to extend Blade?

FYI: I already ran 'php artisan clear-compiled' before every try (and cleared all the application cache), so that's not it.

via Chebli Mohamed