diff --git a/lib/setup.php b/lib/setup.php
index 6d641dd8f19..1fb7796a6a8 100644
--- a/lib/setup.php
+++ b/lib/setup.php
@@ -151,7 +151,9 @@ if (defined('ABORT_AFTER_CONFIG')) {
 }
 
 /** Used by library scripts to check they are being called by Moodle */
-define('MOODLE_INTERNAL', true);
+if (!defined('MOODLE_INTERNAL')) { // necessary because cli installer has to define it earlier
+    define('MOODLE_INTERNAL', true);
+}
 
 /**
  * Database connection. Used for all access to the database.