diff --git a/levels.php b/levels.php
index 599f799..865cce7 100644
--- a/levels.php
+++ b/levels.php
@@ -494,6 +494,7 @@ function level_5_configuration(){
  */
  function level_5_prepare_inbox($level_configuration) {
     global $level_5_coordinates;
+    $expected_outbox = array();
     $level_5_coordinates_copy = $level_5_coordinates;
     $inbox = array();
     for($j = 0; $j < $level_configuration['inbox_size']; $j++){