diff --git a/phpBB/includes/functions_privmsgs.php b/phpBB/includes/functions_privmsgs.php
index c4cbb7ca1e..ec05a2a555 100644
--- a/phpBB/includes/functions_privmsgs.php
+++ b/phpBB/includes/functions_privmsgs.php
@@ -1316,6 +1316,10 @@ function submit_pm($mode, $subject, &$data, $put_in_outbox = true)
 	// Recipient Information
 	$recipients = $to = $bcc = array();
 
+	// First of all make sure the subject are having the correct length.
+	// To achieve this without cutting off between special chars we convert to an array and then count the elements.
+	$subject = truncate_string($subject);
+
 	if ($mode != 'edit')
 	{
 		// Build Recipient List