diff --git a/app/controllers/zipdown_controller.rb b/app/controllers/zipdown_controller.rb
index f0dc157b5..d4699b6c4 100644
--- a/app/controllers/zipdown_controller.rb
+++ b/app/controllers/zipdown_controller.rb
@@ -44,7 +44,9 @@ class ZipdownController < ApplicationController
       if homework != nil
         unless homework.attachments.empty?
           zipfile = zip_homework_by_user homework
-          send_file zipfile, :filename =>  homework.user.user_extensions.student_id + "_" + homework.user.lastname + homework.user.firstname + "_" + homework.name+".zip", :type => detect_content_type(zipfile) if(zipfile)
+          send_file zipfile, :filename =>  (homework.user.user_extensions.student_id.nil? ? "" : homework.user.user_extensions.student_id) +
+              "_" + (homework.user.lastname.nil? ? "" : homework.user.lastname) + (homework.user.firstname.nil? ? "" : homework.user.firstname) +
+              "_" + homework.name + ".zip", :type => detect_content_type(zipfile) if(zipfile)
         else
           render file: 'public/no_file_found.html'
         end
@@ -78,7 +80,7 @@ class ZipdownController < ApplicationController
     homeattach.attachments.each do |attach|
       homeworks_attach_path << attach.diskfile#.to_s.slice((length+1)..-1)
     end
-    zipping("#{homeattach.user.lastname}#{homeattach.user.firstname}_#{homeattach.user.user_extensions.student_id}_#{Time.now.to_i.to_s}.zip", homeworks_attach_path, OUTPUT_FOLDER, true)
+    zipping("#{homeattach.user.lastname}#{homeattach.user.firstname}_#{(homework.user.user_extensions.student_id.nil? ? "" : homework.user.user_extensions.student_id)}_#{Time.now.to_i.to_s}.zip", homeworks_attach_path, OUTPUT_FOLDER, true)
   end