Could not scan for classes inside "src"

I'm getting this error. [RuntimeException] Could not scan for classes inside "src" which does not appear to be a file nor a folder

I have used given default composer.json file with this command composer install

{
    "name": "klaviyo/php-sdk",
    "description": "Klaviyo PHP SDK",
    "keywords": ["klaviyo", "sdk"],
    "type": "library",
    "homepage": "http://github.com/klaviyo",
    "license": "Apache2",
    "authors": [
        {
            "name": "Klaviyo",
            "homepage": "https://github.com/klaviyo"
        }
    ],
    "require": {
        "php": ">=5.2.0",
        "ext-json": "*"
    },
    "autoload": {
        "classmap": ["src"]
    }
}

I'm able to install using this command but I'm not sure about it's reliability. composer require klaviyo/php-sdk @dev

klaviyo / php-klaviyo

Could not scan for classes inside "src" #6