Fatal error conflict with HyperDB

I’m getting the following fatal error when enabling HyperDB version 1.5:

Fatal error: Uncaught W3TC\Util_Environment_Exceptions in /var/www/public_html/wp-content/plugins/w3-total-cache/Root_Environment.php:54 Stack trace: #0 /var/www/public_html/wp-content/plugins/w3-total-cache/Generic_Plugin.php(194): W3TC\Root_Environment->fix_on_event(Object(W3TC\Config), 'first_frontend', Object(W3TC\Config)) #1 /var/www/public_html/wp-includes/class-wp-hook.php(298): W3TC\Generic_Plugin->init('') #2 /var/www/public_html/wp-includes/class-wp-hook.php(323): WP_Hook->apply_filters(NULL, Array) #3 /var/www/public_html/wp-includes/plugin.php(453): WP_Hook->do_action(Array) #4 /var/www/public_html/wp-settings.php(448): do_action('init') #5 /var/www/public_html/wp-config.php(200): require_once('/var/www/vhosts...') #6 /var/www/public_html/wp-load.php(37): require_once('/var/www/vhosts...') #7 /var/www/public_html/wp-blog-header.php(13): require_once('/var/www/vhosts...') #8 /var/www/public_html/index.php(17): require('/var/www/vhosts...') #9 {main} thrown in /var/www/public_html/wp-content/plugins/w3-total-cache/Root_Environment.php on line 54

When I comment out the file w3-total-cache/Generic_Plugin.php lines 193-194, then things work.

Here are the lines in question:

$environment->fix_on_event( $this->_config, 'first_frontend',
	$this->_config );

This is a WordPress multisite install, which is updated to version 4.9.1, and W3TC is updated to version 0.9.6. If I rename HyperDB’s db.php, then things work. Change it back to db.php, then I get the above error message.