Laravel - $ app-> make（）上的分段错误

Question

I have a Service Provider in Laravel which looks like this:

class ImportServiceProvider extends ServiceProvider
{
    protected $importable = [
        \MyApp\Agencies\AgencyImporter::class
    ];

    /**
     * Register the application services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->resolving(Importer::class, function (Importer $importer, $app) {
            foreach($this->importable as $implementation) {
                $importer->attach($app->make($implementation));
            }
        });
    }
}

The idea being, a number of object can be added as Observers to the Importer class when it is instantiated.

However, when I reach this line in the code, I get a Segmentation Fault error:

$app->make($implementation)

However, if I run the code with a hardcoded class before the closure, it works fine:

$app->make(\MyApp\Agencies\AgencyImporter::class);

$this->app->resolving(Importer::class, function (Importer $importer, $app) {
       foreach($this->importable as $implementation) {
            //$importer->attach($app->make($implementation));
       }
  });

So it seems to be issue with the closure. Why this happens?