Weird Route Model Binding

I got this problem in the route with one particular name ("headquarters"): the "show" route has the id parameter in plural, but normally it is in singular.

If I write:

Route::resource('quarters', 'HeadquartersController');  

executing this command line:

php artisan route:list

I get the parameter in singular as expected:

Route::get('/quarters/{quarter}', 'HeadquartersController@show');

But if I write:

Route::resource('headquarters', 'HeadquartersController'); 

executing this command line:

php artisan route:list

I get the parameter in plural:

Route::get('/headquarters/{headquarters}', 'HeadquartersController@show');

via Chebli Mohamed