Can't install 2.5.0 together with PHPUnit 9.x

[jorrit]

This conflict was added to composer.json in version 2.5.0:

    "conflict": {
        "phpunit/php-timer": ">=2"
    }

I am assuming this is because this projects depends on an old version of PHPUnit in order to maintain compatibility with old PHP versions. However, this conflict also applies when used as dependency in my project:

$ composer why-not athari/yalinqo 2.5
athari/yalinqo v2.5.0 conflicts phpunit/php-timer (>=2) 

Unfortunately, there is no conflict-dev setting. Maybe the conflict can be solved in a different way, perhaps by making a specific version of php-timer a direct dev-dependency?