Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 36493)
+++ wp-includes/pluggable.php	(working copy)
@@ -525,7 +525,7 @@
 		return $phpmailer->Send();
 	} catch ( phpmailerException $e ) {
 
-		$mail_error_data = compact( $to, $subject, $message, $headers, $attachments );
+		$mail_error_data = compact( 'to', 'subject', 'message', 'headers', 'attachments' );
 
 		/**
 		 * Fires after a phpmailerException is caught.