diff --git a/core/authorize.php b/core/authorize.php
index c53361848396..69e19098853f 100644
--- a/core/authorize.php
+++ b/core/authorize.php
@@ -154,5 +154,6 @@ else {
 }
 
 if (!empty($output)) {
-  print theme('update_page', array('content' => $output, 'show_messages' => $show_messages));
+  drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
+  print theme('maintenance_page', array('content' => $output, 'show_messages' => $show_messages));
 }
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 9a4f2eef1f76..342c5bcfa5f1 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -3214,9 +3214,6 @@ function drupal_common_theme() {
       'variables' => array('content' => NULL, 'show_messages' => TRUE),
       'template' => 'maintenance-page',
     ),
-    'update_page' => array(
-      'variables' => array('content' => NULL, 'show_messages' => TRUE),
-    ),
     'install_page' => array(
       'variables' => array('content' => NULL),
     ),
diff --git a/core/includes/theme.maintenance.inc b/core/includes/theme.maintenance.inc
index cda4109241c5..578d3544c0fd 100644
--- a/core/includes/theme.maintenance.inc
+++ b/core/includes/theme.maintenance.inc
@@ -159,22 +159,6 @@ function theme_install_page($variables) {
   return theme('maintenance_page', $variables);
 }
 
-/**
- * Returns HTML for the update page.
- *
- * Note: this function is not themeable.
- *
- * @param $variables
- *   An associative array containing:
- *   - content: The page content to show.
- *   - show_messages: Whether to output status and error messages.
- *     FALSE can be useful to postpone the messages to a subsequent page.
- */
-function theme_update_page($variables) {
-  drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
-  return theme('maintenance_page', $variables);
-}
-
 /**
  * Returns HTML for a results report of an operation run by authorize.php.
  *
diff --git a/core/update.php b/core/update.php
index e56d08508f5e..4947d095fdce 100644
--- a/core/update.php
+++ b/core/update.php
@@ -390,7 +390,8 @@ function update_check_requirements($skip_warnings = FALSE) {
     drupal_set_title('Requirements problem');
     $status_report = theme('status_report', array('requirements' => $requirements));
     $status_report .= 'Check the messages and <a href="' . check_url(drupal_requirements_url($severity)) . '">try again</a>.';
-    print theme('update_page', array('content' => $status_report));
+    drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
+    print theme('maintenance_page', array('content' => $status_report));
     exit();
   }
 }
@@ -533,6 +534,7 @@ if (isset($output) && $output) {
     $output->send();
   }
   else {
-    print theme('update_page', array('content' => $output, 'show_messages' => !$progress_page));
+    drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
+    print theme('maintenance_page', array('content' => $output, 'show_messages' => !$progress_page));
   }
 }