jsonSerialize() must be an instance of mixed, array returned

[BohdanParkhomenko]

php-queuesadilla/src/josegonzalez/Queuesadilla/Job/Base.php

Line 86 in 0869282

public function jsonSerialize(): mixed

When I use josegonzalez/cakephp-queuesadilla with php7.4 I get an error

[TypeError] Return value of josegonzalez\Queuesadilla\Job\Base::jsonSerialize() must be an instance of josegonzalez\Queuesadilla\Job\mixed, array returned in vendor/josegonzalez/queuesadilla/src/josegonzalez/Queuesadilla/Job/Base.php on line 89