XF 1.5 How do I enable automatic serialization in our cache?

[Stuart Wright]

Following this thread
https://xenforo.com/community/threa...g-or-set-automatic_serialization-true.105501/
in which Mike suggests enabling automatic serialization (American spelling - urgh) in our config.
Searched here and found this
https://xenforo.com/community/threads/digital-point-image-proxy-paid.66345/page-2#post-698070
and put this

$config['cache']['frontendOptions']['automatic_serialization'] = true;

in my config file but then got this error on screen on every page

An exception occurred: unserialize() expects parameter 1 to be string, array given in /home/sites/avforums/public_html/library/XenForo/Model/DataRegistry.php on line 117

1. XenForo_Application::handlePhpError()
2. unserialize() in XenForo/Model/DataRegistry.php at line 117
3. XenForo_Model_DataRegistry->getMulti() in XenForo/Dependencies/Abstract.php at line 147
4. XenForo_Dependencies_Abstract->preLoadData() in XenForo/FrontController.php at line 127
5. XenForo_FrontController->run() in /home/sites/avforums/public_html/index.php at line 13

so I removed it pretty quickly!
How do I enable automatic serialisation in my config, please?

 

[Mike]

As I believe was mentioned elsewhere, if you're changing cache config like that, you need to purge your cache after the change.