diff --git a/phpBB/includes/acp/acp_board.php b/phpBB/includes/acp/acp_board.php
index cd72a8748a..32f84218df 100644
--- a/phpBB/includes/acp/acp_board.php
+++ b/phpBB/includes/acp/acp_board.php
@@ -549,8 +549,8 @@ class acp_board
 			}
 		}
 
-		// Invalidate the text_formatter cache when posting options are changed
-		if ($mode == 'post' && $submit)
+		// Invalidate the text_formatter cache when posting or server options are changed
+		if (preg_match('(^(?:post|server)$)', $mode) && $submit)
 		{
 			$phpbb_container->get('text_formatter.cache')->invalidate();
 		}