# Bug in mu-plugins/kinsta-mu-plugins on Astra theme update

**URL:** <https://community.kinsta.com/t/bug-in-mu-plugins-kinsta-mu-plugins-on-astra-theme-update/5861>\
**Category:** Feedback\
**Created:** [January 6, 2026, 1:46pm UTC](https://community.kinsta.com/t/bug-in-mu-plugins-kinsta-mu-plugins-on-astra-theme-update/5861 "2026-01-06T13:46:09Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![rtpHarry](https://avatars.discourse-cdn.com/v4/letter/r/3be4f8/32.png) [@rtpHarry](https://community.kinsta.com/u/rtpHarry)\
**Post date:** [January 6, 2026, 1:46pm UTC](https://community.kinsta.com/t/bug-in-mu-plugins-kinsta-mu-plugins-on-astra-theme-update/5861/1 "2026-01-06T13:46:09Z")

</div>

I saw this error bubble up today:

```plaintext
2026.01.06. 12:56:14
[error] 86494#86494: *1800216 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught TypeError: in_array(): Argument #2 ($haystack) must be of type array, null given in /www/knepp_839/public/wp-content/mu-plugins/kinsta-mu-plugins/app/Cache/Autopurge/WPThemeController.php:25
2026.01.06. 12:56:14
Stack trace:
2026.01.06. 12:56:14
#0 /www/knepp_839/public/wp-content/mu-plugins/kinsta-mu-plugins/app/Cache/Autopurge/WPThemeController.php(25): in_array('knepp', NULL, true)
2026.01.06. 12:56:14
#1 /www/knepp_839/public/wp-includes/class-wp-hook.php(341): Kinsta\KMP\Cache\Autopurge\WPThemeController->{closure:Kinsta\KMP\Cache\Autopurge\WPThemeController::hook():17}(Object(Theme_Upgrader), Array)
2026.01.06. 12:56:14
#2 /www/knepp_839/public/wp-includes/class-wp-hook.php(365): WP_Hook->apply_filters(NULL, Array)
2026.01.06. 12:56:14
#3 /www/knepp_839/public/wp-includes/plugin.php(522): WP_Hook->do_action(Array)
2026.01.06. 12:56:14
#4 /www/knepp_839/public/wp-admin/includes/class-wp-upgrader.php(987): do_action('upgrader_proces...', Object(Theme_Upgrader), Array)
2026.01.06. 12:56:14
#5 /www/knepp_839/public/wp-admin/includes/class-theme-upgrader.php(324): WP_Upgrader->run(Array)

```

I have Astra as the theme and I upgrade it via the link it injects where, after you update the plugin, it puts a notice saying “update theme if not already done so”.

The link that it injects into that goes directly to the install / update process. At the end it showed a fatal error, underneath the normal “installing…” type messages.

The site didn’t go down, so its a minor thing but obviously that is sending some data in an unexpected way.

Probably a pretty simple fix if you throw it at an AI, so I thought I would share it here.

---

<div class="post-metadata">

**Author:** ![Adrian\_L](https://sea2.discourse-cdn.com/flex020/user_avatar/community.kinsta.com/adrian_l/32/2810_2.png) [@Adrian\_L](https://community.kinsta.com/u/Adrian_L)\
**Post date:** [January 7, 2026, 12:02am UTC](https://community.kinsta.com/t/bug-in-mu-plugins-kinsta-mu-plugins-on-astra-theme-update/5861/2 "2026-01-07T00:02:13Z")

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Thanks for the report @rtpHarry . Can you confirm the current version of the Kinsta MU plugin the site is using? Also, is the site using a WP Pusher plugin? Thanks!