Declaration of LaminasStdlibArrayObject::offsetExists(LaminasStdlibmixed $key) error after updating to 2.4.5-p1

After updating from Magento 2.4.4 running on PHP 7.4 to Magento 2.4.5-p1 running on PHP 8.1 I am getting this error:

Declaration of LaminasStdlibArrayObject::offsetExists(LaminasStdlibmixed $key) must be compatible with ArrayAccess::offsetExists($offset)

Any idea what the reason might be? The update went through normally, also the compilation and the deployment. I checked the vendor/laminas folder and its contents and it all have a current date, so it looks like it has been updated properly.

Any idea how to go on here?

Thanks!