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
@@ -1019,7 +1019,7 @@
   $driver = $form_state['values']['driver'];
   $database = $form_state['values'][$driver];
   $drivers = drupal_get_database_types();
-  if (substr(get_class($drivers[$driver]), 0, 11) !== 'Drupal\\Core') {
+  if (strpos(get_class($drivers[$driver]), 'Drupal\\Core\\Database') !== 0) {
     $database['custom'] = TRUE;
   }
   $database['driver'] = $driver;