diff --git a/webform_report.inc b/webform_report.inc
index bcc4901..7d9d01b 100644
--- a/webform_report.inc
+++ b/webform_report.inc
@@ -1406,6 +1406,8 @@ function webform_report_export_form_submit($form_id, $form_state) {
     drupal_set_header('Content-Type: ' . $ctype);
     drupal_set_header('Content-Length: ' . strlen($output));
     drupal_set_header('Content-Disposition: attachment; filename="' . $fname . '"');
+    // Allow Internet Explorer to download Excel files over HTTPS
+    drupal_set_header('Cache-Control: private, must-revalidate');
     echo $output;
     die();
   }