diff --git a/phpBB/install/app.php b/phpBB/install/app.php
index 0e6212e37a..36d16e914b 100644
--- a/phpBB/install/app.php
+++ b/phpBB/install/app.php
@@ -16,7 +16,10 @@
  */
 define('IN_PHPBB', true);
 define('IN_INSTALL', true);
-define('PHPBB_ENVIRONMENT', 'production');
+if (!defined('PHPBB_ENVIRONMENT'))
+{
+	define('PHPBB_ENVIRONMENT', 'production');
+}
 $phpbb_root_path = '../';
 $phpEx = substr(strrchr(__FILE__, '.'), 1);