Problem with routes with alias in laravel 5.1

I am having problems creating routes with aliases in Laravel, I can use normal routes, however, when I add an alias in the route as:

Route::get('admin/categories', ['as'=>'categoria','uses'=>'AdminCategoriesController@index']);

Sorry, the page you are looking for could not be found.
1/1 NotFoundHttpException in RouteCollection.php line 161:

    in RouteCollection.php line 161
    at RouteCollection->match(object(Request)) in Router.php line 750
    at Router->findRoute(object(Request)) in Router.php line 659
    at Router->dispatchToRoute(object(Request)) in Router.php line 635
    at Router->dispatch(object(Request)) in Kernel.php line 236
    at Kernel->Illuminate\Foundation\Http\{closure}(object(Request))
    at call_user_func(object(Closure), object(Request)) in Pipeline.php line 139
    at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in VerifyCsrfToken.php line 50
    at VerifyCsrfToken->handle(object(Request), object(Closure))
    at call_user_func_array(array(object(VerifyCsrfToken), 'handle'), array(object(Request), object(Closure))) in Pipeline.php line 124
    at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in ShareErrorsFromSession.php line 49
    at ShareErrorsFromSession->handle(object(Request), object(Closure))
    at call_user_func_array(array(object(ShareErrorsFromSession), 'handle'), array(object(Request), object(Closure))) in Pipeline.php line 124
    at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in StartSession.php line 62
    at StartSession->handle(object(Request), object(Closure))
    at call_user_func_array(array(object(StartSession), 'handle'), array(object(Request), object(Closure))) in Pipeline.php line 124
    at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in AddQueuedCookiesToResponse.php line 37
    at AddQueuedCookiesToResponse->handle(object(Request), object(Closure))
    at call_user_func_array(array(object(AddQueuedCookiesToResponse), 'handle'), array(object(Request), object(Closure))) in Pipeline.php line 124
    at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in EncryptCookies.php line 59
    at EncryptCookies->handle(object(Request), object(Closure))
    at call_user_func_array(array(object(EncryptCookies), 'handle'), array(object(Request), object(Closure))) in Pipeline.php line 124
    at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in CheckForMaintenanceMode.php line 44
    at CheckForMaintenanceMode->handle(object(Request), object(Closure))
    at call_user_func_array(array(object(CheckForMaintenanceMode), 'handle'), array(object(Request), object(Closure))) in Pipeline.php line 124
    at Pipeline->Illuminate\Pipeline\{closure}(object(Request))
    at call_user_func(object(Closure), object(Request)) in Pipeline.php line 103
    at Pipeline->then(object(Closure)) in Kernel.php line 122
    at Kernel->sendRequestThroughRouter(object(Request)) in Kernel.php line 87
    at Kernel->handle(object(Request)) in index.php line 54

My .htaccess file

<IfModule mod_rewrite.c>
    <IfModule mod_negotiation.c>
        Options -MultiViews
    </IfModule>

    RewriteEngine On


    # Redirect Trailing Slashes If Not A Folder...
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)/$ /$1 [L,R=301]

    # Handle Front Controller...
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteRule ^ index.php [L]
</IfModule>