diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index be8c695..e808a87 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -547,6 +547,17 @@ function drupal_settings_initialize() {
   }
 
   new Settings(isset($settings) ? $settings : array());
+  // If Drupal is behind a reverse proxy or load balancer that is communicating
+  // with the end-user over https but with Drupal over http we will generate a
+  // broken $base_path unless we set $_SERVER['HTTPS'] to 'on'. Trusting these
+  // headers is a potential security risk so we only do so if
+  // $settings['reverse_proxy'] has been set.
+  if (settings()->get('reverse_proxy')) {
+    // X-Forwarded-Proto is the most common convention for protocol information.
+    if (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && strtolower($_SERVER['HTTP_X_FORWARDED_PROTO']) === 'https') {
+      $_SERVER['HTTPS'] = 'on';
+    }
+  }
   $is_https = isset($_SERVER['HTTPS']) && strtolower($_SERVER['HTTPS']) == 'on';
 
   if (isset($base_url)) {