Clean Talk causing critical issue

I’m getting WordPress critical error issues, and the automatic WordPress critical error emails seem to indicate that the error is being caused by Clean Talk. Can you help me figure out what is causing the error and how to fix it?

Here is the error log(I replaced our domain file structure with “redacted”):
WordPress version 6.4.3
Current plugin: Anti-Spam by CleanTalk (version 6.26)
PHP version 8.1.27 Error Details

An error of type E_ERROR was caused in line 43 of the file /var/www/redacted/wp-content/plugins/cleantalk-spam-protect/lib/Cleantalk/ApbctWP/Helper.php. Error message: Uncaught Error: Undefined constant “Cleantalk\ApbctWP\CURLOPT_USERAGENT” in /var/www/redacted/wp-content/plugins/cleantalk-spam-protect/lib/Cleantalk/ApbctWP/Helper.php:43
Stack trace: 0 /var/www/redacted/wp-content/plugins/cleantalk-spam-protect/lib/Cleantalk/ApbctWP/Helper.php(162): Cleantalk\ApbctWP\Helper::httpRequest() 1 /var/www/redacted/wp-content/plugins/cleantalk-spam-protect/cleantalk.php(1243): Cleantalk\ApbctWP\Helper::httpRequestRcToHostTest() 2 [internal function]: apbct_sfw_update__init() 3 /var/www/redacted/wp-content/plugins/cleantalk-spam-protect/lib/Cleantalk/Common/Cron.php(265): call_user_func_array() 4 /var/www/redacted/wp-content/plugins/cleantalk-spam-protect/cleantalk.php(221): Cleantalk\Common\Cron->runTasks() 5 /var/www/redacted/wp-includes/class-wp-hook.php(324): {closure}() 6 /var/www/redacted/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() 7 /var/www/redacted/wp-includes/plugin.php(517): WP_Hook->do_action() 8 /var/www/redacted/wp-settings.php(643): do_action() 9 /var/www/redacted/wp-config.php(132): require_once(‘…’) 10 /var/www/redacted/wp-load.php(50): require_once(‘…’) 11 /var/www/redacted/wp-admin/admin-ajax.php(22): require_once(‘…’) 12 {main}

thrown