diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 882a049..621dafa 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -2195,6 +2195,36 @@ function system_update_8051() {
 }
 
 /**
+ * Update variables to $settings.
+ */
+function system_update_8052() {
+  $upgrade = array(
+    'proxy_server',
+    'proxy_port',
+    'proxy_username',
+    'proxy_password',
+    'proxy_user_agent',
+    'proxy_exceptions',
+    'reverse_proxy',
+    'reverse_proxy_addresses',
+    'reverse_proxy_header',
+    'omit_vary_cookie',
+  );
+
+  foreach ($upgrade as $variable_name => $setting_name) {
+    $variable = update_variable_get($variable_name, '');
+    if ($variable) {
+      $settings['settings'][$setting_name] = (object) array(
+        'value' => $variable,
+        'required' => TRUE,
+      );
+    }
+  }
+
+  drupal_rewrite_settings($settings);
+}
+
+/**
  * @} End of "defgroup updates-7.x-to-8.x".
  * The next series of updates should start at 9000.
  */