diff --git a/phpBB/includes/acp/acp_board.php b/phpBB/includes/acp/acp_board.php
index 41849b909a..008594a319 100644
--- a/phpBB/includes/acp/acp_board.php
+++ b/phpBB/includes/acp/acp_board.php
@@ -437,7 +437,7 @@ class acp_board
 		// We go through the display_vars to make sure no one is trying to set variables he/she is not allowed to...
 		foreach ($display_vars['vars'] as $config_name => $null)
 		{
-			if ($null === false || strpos($config_name, 'legend') !== false)
+			if (!isset($cfg_array[$config_name]) || strpos($config_name, 'legend') !== false)
 			{
 				continue;
 			}