diff --git a/app/controllers/zipdown_controller.rb b/app/controllers/zipdown_controller.rb
index 2a4430935..d66c6a30d 100644
--- a/app/controllers/zipdown_controller.rb
+++ b/app/controllers/zipdown_controller.rb
@@ -17,6 +17,7 @@ class ZipdownController < ApplicationController
       begin
         if params[:base64file]
           file = Base64.decode64(params[:base64file])
+          file = file.sub('*', '+')
           send_file "#{OUTPUT_FOLDER}/#{file}", :filename => filename_for_content_disposition(file), :type => detect_content_type(file)
         else
           send_file "#{OUTPUT_FOLDER}/#{params[:file]}", :filename => filename_for_content_disposition(params[:filename]), :type => detect_content_type(params[:file])
@@ -118,11 +119,15 @@ class ZipdownController < ApplicationController
     [{files:[out_file.file_path], count: 1, index: 1,
       real_file: out_file.file_path,
       file: File.basename(out_file.file_path),
-      base64file: Base64.encode64(File.basename(out_file.file_path)),
+      base64file: encode64(File.basename(out_file.file_path)),
       size:(out_file.pack_size / 1024.0 / 1024.0).round(2)
      }]
   end
 
+  def encode64(str)
+    Base64.encode64(str).sub('+', '*')
+  end
+
   def zip_homework_common homework_common
     bid_homework_path = []
     digests = []
@@ -142,7 +147,7 @@ class ZipdownController < ApplicationController
     [{files:[out_file.file_path], count: 1, index: 1,
       real_file: out_file.file_path,
       file: File.basename(out_file.file_path),
-      base64file: Base64.encode64(File.basename(out_file.file_path)),
+      base64file: encode64(File.basename(out_file.file_path)),
       size:(out_file.pack_size / 1024.0 / 1024.0).round(2)
      }]
   end