diff --git a/comment_notify.module b/comment_notify.module
index 17353e397ddcb68a0ba4d367a69d6e0dcc12c82a..7b89f91e2b3dddad811c713d2cf3644c988e3620 100644
--- a/comment_notify.module
+++ b/comment_notify.module
@@ -392,6 +392,9 @@ function _comment_notify_mailalert(CommentInterface $comment) {
     if ($comment_account = user_load_by_name($comment->getAuthorName())) {
       $comment_mail = $comment_account->getEmail() ?: '';
     }
+    else {
+      $comment_mail = '';
+    }
   }
   else {
     $comment_mail = $comment->getAuthorEmail();