diff --git a/app/controllers/submissions_controller.rb b/app/controllers/submissions_controller.rb
index 60e52253..d7c89506 100644
--- a/app/controllers/submissions_controller.rb
+++ b/app/controllers/submissions_controller.rb
@@ -76,7 +76,7 @@ class SubmissionsController < ApplicationController
     stringio = Zip::OutputStream.write_buffer do |zio|
       @files.each do |file|
         zio.put_next_entry(file.path.to_s == '' ? file.name_with_extension : File.join(file.path, file.name_with_extension))
-        zio.write(file.content)
+        zio.write(file.content.present? ? file.content : file.native_file.read)
       end
 
       # zip exercise description