diff --git a/phpBB/includes/acp/acp_language.php b/phpBB/includes/acp/acp_language.php
index 423ced43e0..2c4e4f71f6 100644
--- a/phpBB/includes/acp/acp_language.php
+++ b/phpBB/includes/acp/acp_language.php
@@ -960,6 +960,8 @@ if (empty($lang) || !is_array($lang))
 
 // DEVELOPERS PLEASE NOTE
 //
+// All language files should use UTF-8 as their encoding and the files must not contain a BOM.
+//
 // Placeholders can now contain order information, e.g. instead of
 // \'Page %s of %s\' you can (and should) write \'Page %1$s of %2$s\', this allows
 // translators to re-order the output of data while ensuring it remains correct