diff -u b/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
--- b/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -727,7 +727,7 @@
   global $base_url, $base_path, $base_root, $script_path;
 
   // Export these settings.php variables to the global namespace.
-  global $cookie_domain, $conf, $installed_profile, $drupal_hash_salt, $is_https, $base_secure_url, $base_insecure_url, $config_directories;
+  global $databases, $cookie_domain, $conf, $installed_profile, $drupal_hash_salt, $is_https, $base_secure_url, $base_insecure_url, $config_directories;
   $conf = array();
 
   // Make conf_path() available as local variable in settings.php.
@@ -2303,7 +2303,8 @@
   // installed yet (i.e., if no $databases array has been defined in the
   // settings.php file) and we are not already installing.
   $databases = settings()->get('databases');
-  if (empty($databases) && !drupal_installation_attempted()) {
+  $databases_d7 = $GLOBALS['databases'];
+  if (empty($databases) && empty($databases_d7) && !drupal_installation_attempted()) {
     include_once DRUPAL_ROOT . '/core/includes/install.inc';
     install_goto('core/install.php');
   }
diff -u b/core/includes/install.core.inc b/core/includes/install.core.inc
--- b/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -416,8 +416,7 @@
     $task = NULL;
 
     // Do not install over a configured settings.php.
-    $databases = settings()->get('databases');
-    if (!empty($databases)) {
+    if (!empty($GLOBALS['databases'])) {
       throw new Exception(install_already_done_error());
     }
   }
@@ -429,7 +428,8 @@
     $task = NULL;
 
     // Do not install over a configured settings.php.
-    if (!empty($GLOBALS['databases'])) {
+    $databases = settings()->get('databases');
+    if (!empty($databases)) {
       throw new Exception(install_already_done_error());
     }
   }
@@ -949,7 +949,7 @@
  * Verifies that settings.php specifies a valid database connection.
  */
 function install_verify_database_settings() {
-  $databases = settings()->get('databases');
+  global $databases;
   if (!empty($databases)) {
     $database = $databases['default']['default'];
     drupal_static_reset('conf_path');
@@ -961,7 +961,7 @@
  * Verifies that settings.php specifies a valid database connection.
  */
 function install_verify_database_settings() {
-  global $databases;
+  $databases = settings()->get('databases');
   if (!empty($databases)) {
     $database = $databases['default']['default'];
     drupal_static_reset('conf_path');
@@ -973,7 +973,7 @@
  * @ingroup forms
  */
 function install_settings_form($form, &$form_state, &$install_state) {
-  $databases = settings()->get('databases');
+  global $databases;
   $profile = $install_state['parameters']['profile'];
 
   drupal_static_reset('conf_path');
@@ -985,7 +985,7 @@
  * @ingroup forms
  */
 function install_settings_form($form, &$form_state, &$install_state) {
-  global $databases;
+  $databases = settings()->get('databases');
   $profile = $install_state['parameters']['profile'];
 
   drupal_static_reset('conf_path');
@@ -1062,6 +1062,7 @@
  * Checks a database connection and returns any errors.
  */
 function install_database_errors($database, $settings_file) {
+  global $databases;
   $errors = array();
 
   // Check database type.
@@ -1073,7 +1074,6 @@
  * Checks a database connection and returns any errors.
  */
 function install_database_errors($database, $settings_file) {
-  global $databases;
   $errors = array();
 
   // Check database type.
only in patch2:
unchanged:
--- a/core/includes/install.inc
+++ b/core/includes/install.inc
@@ -373,6 +373,9 @@ function _drupal_rewrite_settings_global(&$ref, $variable) {
   if (is_object($variable)) {
     $ref = $variable->value;
   }
+  elseif (is_scalar($variable)) {
+    $ref = $variable;
+  }
   else {
     foreach ($variable as $k => $v) {
       _drupal_rewrite_settings_global($ref[$k], $v);
@@ -400,6 +403,9 @@ function _drupal_rewrite_settings_dump($variable, $variable_name) {
       $return .= _drupal_rewrite_settings_dump_one($variable, "$variable_name = ", "\n");
     }
   }
+  elseif (is_scalar($variable)) {
+    $return .= _drupal_rewrite_settings_dump_one($variable, "$variable_name = $variable;\n");
+  }
   else {
     foreach ($variable as $k => $v) {
       $return .= _drupal_rewrite_settings_dump($v, $variable_name . "['" . $k . "']");
only in patch2:
unchanged:
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -92,9 +92,14 @@ function update_check_incompatibility($name, $type = 'module') {
 function update_prepare_d8_bootstrap() {
   include_once DRUPAL_ROOT . '/core/includes/install.inc';
   include_once DRUPAL_ROOT . '/core/includes/schema.inc';
+
   // Bootstrap to configuration.
   drupal_bootstrap(DRUPAL_BOOTSTRAP_CONFIGURATION);
 
+  // Update the db settings.
+  $settings['settings']['databases'] = isset($GLOBALS['databases']) ? $GLOBALS['databases'] : array();
+  drupal_rewrite_settings($settings);
+
   // During the bootstrap to DRUPAL_BOOTSTRAP_PAGE_CACHE, code will try to read
   // the cache but the cache tables are not compatible yet. Use the Null backend
   // by default to avoid exceptions.