Upgrade to Laravel 5.6 from 5.5 [duplicate]

This question already has an answer here:

• Upgrading Laravel 5.5 to 5.6 error 4 answers

I have one little problem after updating my Laravel 5.5 project to 5.6.

All packages is was successful updated.

But one package is still have issue.

Console result:

Your requirements could not be resolved to an installable set of packages.
Problem 1
- The requested package fideloper/proxy ~4.0 is satisfiable by fideloper/proxy[4.0.x-dev] but these conflict with your requirements or minimum-stability.

But i already define 4.0 version in my composer.json

    "require": {
    "php": ">=7.1.3",
    "fideloper/proxy": "~4.0",
    "laravel/framework": "5.6.*",
    "laravel/tinker": "~1.0"
},

And add 2 line in composer.json

    "minimum-stability":"dev",
    "prefer-stable": true

And after make autoload command:

composer dump-autoload

This error is appear:

> Illuminate\Foundation\ComposerScripts::postAutoloadDump

@php artisan package:discover

In trustedproxy.php line 66:                                        
Undefined class constant 'HEADER_CLIENT_IP'  
Script @php artisan package:discover handling the post-autoload-dump event returned with error code 1

Are there any suggestions? Thanks in advance.

via Chebli Mohamed