Laravel 4.2 Composer install error: "Failed to scan for classes"

I want to install multiple packages on my fresh Laravel 4.2 installation via Composer. However, I am getting an exception.

This is my Composer file:

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "license": "MIT",   
    "require": {
        "laravel/framework": "4.2.*",
        "zizaco/confide": "~4.0@dev",
        "zizaco/entrust": "1.2.*@dev",
        "barryvdh/laravel-ide-helper": "1.*",
        "fzaninotto/faker": "1.3.*@dev",
        "bllim/datatables": "~1.3",
        "barryvdh/laravel-debugbar": "~1.7"
    },
    "require-dev": {
        "way/generators": "~2.6",
        "barryvdh/laravel-ide-helper": "~1.11"
    },
    "autoload": {
        "classmap": [
            "app/commands",
            "app/controllers",
            "app/models",
            "app/database/migrations",
            "app/database/seeds",
            "app/tests/TestCase.php",
            "app/controllers/admin",
            "app/controllers/user"
        ]
    },
    "scripts": {
        "post-install-cmd": [
            "php artisan clear-compiled",
            "php artisan optimize"
        ],
        "post-update-cmd": [
            "php artisan clear-compiled",
            "php artisan optimize"
        ],
        "post-update-cmd":[
            "php artisan ide-helper:generate"
        ],
        "post-create-project-cmd": [
            "php artisan key:generate"
        ]
    },
    "config": {
        "preferred-install": "dist"
    },
    "minimum-stability": "stable"
}

      

        
        
        
      

    

On startup, composer install

I get:

$ composer install
Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Warning: The lock file is not up to date with the latest changes in composer.jso
n. You may be getting outdated dependencies. Run update to update them.
Nothing to install or update
Generating autoload files



  [RuntimeException]
  Could not scan for classes inside "app/controllers/admin" which does not ap
  pear to be a file nor a folder



install [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--no-p
lugins] [--no-custom-installers] [--no-scripts] [--no-progress] [-v|vv|vvv|--ver
bose] [-o|--optimize-autoloader] [packages1] ... [packagesN]

      

        
        
        
      

    

This is basically a fresh install of Laravel. Why am I getting the error:

Could not scan for classes inside "app/controllers/admin" which does not appear to be a file nor a folder

      

        
        
        
      

    

UPDATE

Usage composer update

:

$ composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Removing mockery/mockery (0.9.2)
  - Removing phpunit/phpunit (4.3.4)
  - Removing phpunit/php-code-coverage (2.0.11)
  - Removing phpunit/php-token-stream (1.3.0)
  - Removing phpunit/php-file-iterator (1.3.4)
  - Removing phpunit/php-timer (1.0.5)
  - Removing phpunit/phpunit-mock-objects (2.3.0)
  - Removing phpunit/php-text-template (1.2.0)
  - Removing doctrine/instantiator (1.0.4)
  - Removing symfony/yaml (v2.5.6)
  - Removing sebastian/comparator (1.0.1)
  - Removing sebastian/diff (1.2.0)
  - Removing sebastian/environment (1.2.0)
  - Removing sebastian/exporter (1.0.2)
  - Removing sebastian/version (1.0.3)
  - Removing summerstreet/woodling (v0.1.6)
Writing lock file
Generating autoload files



  [RuntimeException]
  Could not scan for classes inside "app/controllers/admin" which does not ap
  pear to be a file nor a folder



update [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--lock]
 [--no-plugins] [--no-custom-installers] [--no-scripts] [--no-progress] [--with-
dependencies] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [packages1] ... [
packagesN]