Installing laravolt/avatar I got error method Laravolt\Avatar\Facade::isDeferred - laravel

Question

I tried to install /laravolt/avatar pluging in my laravel 6 app and got error while installing:
$ composer require laravolt/avatar
Using version ^3.0 for laravolt/avatar
In ProviderRepository.php line 149:
...
Call to undefined method Laravolt\Avatar\Facade::isDeferred()
Script #php artisan package:discover --ansi handling the post-autoload-dump event returned with error code 1
At https://github.com/laravolt/avatar site I see last updates 5 days ago and I suppose it is not absolute ?
File composer.json of my project :
{
"name": "laravel/laravel",
"type": "project",
"description": "The Laravel Framework.",
"keywords": [
"framework",
"laravel"
],
"license": "MIT",
"require": {
"php": "^7.2",
"fideloper/proxy": "^4.0",
"laravel/framework": "^6.2",
"laravel/helpers": "^1.1",
"laravel/passport": "^8.1",
"laravel/tinker": "^2.0",
"laravolt/avatar": "^3.0"
},
"require-dev": {
"facade/ignition": "^1.4",
"fzaninotto/faker": "^1.4",
"laravel/ui": "^1.1",
"mockery/mockery": "^1.0",
"nunomaduro/collision": "^3.0",
"phpunit/phpunit": "^8.0"
},
"config": {
"optimize-autoloader": true,
"preferred-install": "dist",
"sort-packages": true
},
"extra": {
"laravel": {
"dont-discover": []
}
},
"autoload": {
"psr-4": {
"App\\": "app/"
},
"classmap": [
"database/seeds",
"database/factories"
]
},
"autoload-dev": {
"psr-4": {
"Tests\\": "tests/"
}
},
"minimum-stability": "dev",
"prefer-stable": true,
"scripts": {
"post-autoload-dump": [
"Illuminate\\Foundation\\ComposerScripts::postAutoloadDump",
"#php artisan package:discover --ansi"
],
"post-root-package-install": [
"#php -r \"file_exists('.env') || copy('.env.example', '.env');\""
],
"post-create-project-cmd": [
"#php artisan key:generate --ansi"
]
}
}
Why I have error and how to fix it ?
I searched in net and did not find how to fix it ?
Thanks!