diff --git a/src/routes/mailboxes.js b/src/routes/mailboxes.js
index ed6464319..a2d2bc2c6 100644
--- a/src/routes/mailboxes.js
+++ b/src/routes/mailboxes.js
@@ -71,7 +71,7 @@ function setAliases(req, res, next) {
 
     mailboxes.setAliases(req.params.mailboxId, req.body.aliases, function (error) {
         if (error && error.reason === MailboxError.NOT_FOUND) return next(new HttpError(404, 'No such mailbox'));
-        if (error && error.reason === MailboxError.BAD_FIELD) return next(new HttpError(400, error.reason));
+        if (error && error.reason === MailboxError.BAD_FIELD) return next(new HttpError(400, error.message));
         if (error && error.reason === MailboxError.ALREADY_EXISTS) return next(new HttpError(409, 'One or more alias already exist'));
         if (error) return next(new HttpError(500, error));