diff --git a/app/models/dmsf_file.rb b/app/models/dmsf_file.rb
index be37bdbd..b80eb0e9 100644
--- a/app/models/dmsf_file.rb
+++ b/app/models/dmsf_file.rb
@@ -621,7 +621,7 @@ class DmsfFile < ApplicationRecord
     if locked_for_user?
       return l(:title_locked_by_user, user: lock.reverse[0].user) if lock.reverse[0].user
 
-      return l(:notice_account_unknown_email)
+      return "#{l(:label_user)} #{l('activerecord.errors.messages.invalid')}"
     end
     l(:title_unlock_file)
   end