diff --git a/phpBB/includes/functions_posting.php b/phpBB/includes/functions_posting.php
index df5de6230a..f5271672a4 100644
--- a/phpBB/includes/functions_posting.php
+++ b/phpBB/includes/functions_posting.php
@@ -834,7 +834,7 @@ function posting_gen_attachment_entry($attachment_data, &$filename_data, $show_a
 		'FILESIZE'						=> $config['max_filesize'],
 		'FILE_COMMENT'					=> (isset($filename_data['filecomment'])) ? $filename_data['filecomment'] : '',
 		'MAX_ATTACHMENT_FILESIZE'		=> $config['max_filesize'] > 0 ? $user->lang('MAX_ATTACHMENT_FILESIZE', get_formatted_filesize($config['max_filesize'])) : '',
-		'ALLOWED_ATTACHMENTS'			=> !empty($allowed_attachments) ? implode(',', $allowed_attachments) : '',
+		'ALLOWED_ATTACHMENTS'			=> !empty($allowed_attachments) ? '.' . implode(',.', $allowed_attachments) : '',
 	];
 
 	/**