diff --git a/server/app/controllers/analyses_controller.rb b/server/app/controllers/analyses_controller.rb
index 2bb12bae5..e9f442a64 100644
--- a/server/app/controllers/analyses_controller.rb
+++ b/server/app/controllers/analyses_controller.rb
@@ -727,6 +727,8 @@ def download_BTAP_results_zip
     path = "/mnt/openstudio/server/assets/results.#{@analysis.id}.zip";
 
     if File.exist?(path)
+      file_size = File.size(path)
+      response.headers['Content-Length'] = file_size.to_s
       send_data File.open(path, 'rb').read, filename: "results.#{@analysis.id}.zip", type: "application/zip", disposition: 'attachment'
     end
   end