diff --git a/phpBB/phpbb/install/module/install_database/task/add_config_settings.php b/phpBB/phpbb/install/module/install_database/task/add_config_settings.php
index 20b7679ec1..7a2df01de6 100644
--- a/phpBB/phpbb/install/module/install_database/task/add_config_settings.php
+++ b/phpBB/phpbb/install/module/install_database/task/add_config_settings.php
@@ -129,12 +129,19 @@ class add_config_settings extends \phpbb\install\task_base
 		$this->db->sql_return_on_error(true);
 
 		$server_name	= $this->install_config->get('server_name');
-		$cookie_domain	= $this->install_config->get('cookie_domain');
 		$current_time 	= time();
 		$user_ip		= phpbb_ip_normalise($this->iohandler->get_server_variable('REMOTE_ADDR'));
 		$user_ip		= ($user_ip === false) ? '' : $user_ip;
 		$referer		= $this->iohandler->get_server_variable('REFERER');
 
+		// Calculate cookie domain
+		$cookie_domain = $server_name;
+
+		if (strpos($cookie_domain, 'www.') === 0)
+		{
+			$cookie_domain = substr($cookie_domain, 3);
+		}
+
 		// Set default config and post data, this applies to all DB's
 		$sql_ary = array(
 			'INSERT INTO ' . $this->config_table . " (config_name, config_value)