diff --git a/phpBB/includes/smtp.php b/phpBB/includes/smtp.php
index 279e4332b9..da5f62be6f 100644
--- a/phpBB/includes/smtp.php
+++ b/phpBB/includes/smtp.php
@@ -86,7 +86,7 @@ function smtpmail($mail_to, $subject, $message, $headers = '')
 				$bcc = preg_replace('#^bcc:(.*)#si', '\1', $header);
 				$header = '';
 			}
-			$headers .= $header . "\r\n";
+			$headers .= ($header != '') ? $header . "\r\n" : '';
 		}
 
 		$headers = chop($headers);