Permission Cache with Redis does not seems to work?

[khangphung-vl]

Hi everyone,
I already successfully setup Redis cache for spatie permission, as I enter the page as an User with role, a new Redis key-value is added with the key is in the following format
redis_prefix + cache_prefix + "spatie.permission.cache"
Which seems to be correct (per the documentation description). But the value of the inserted key is a:3:{s:5:"alias";a:0:{}s:11:"permissions";a:0:{}s:5:"roles";a:0:{}} (which is a PHP serialized), and can be translated to
{ "alias": [], "permissions": [], "roles": [] }

Basically, it is empty. What is going on and is this an expected behavior?