Index: includes/environment.inc
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/drush/includes/environment.inc,v
retrieving revision 1.102
diff -u -p -r1.102 environment.inc
--- includes/environment.inc    14 Nov 2010 14:47:10 -0000      1.102
+++ includes/environment.inc    22 Dec 2010 03:12:25 -0000
@@ -1126,6 +1126,12 @@ function drush_valid_db_credentials() {
       break;
     case 7:
     default:
+      if (file_exists("./includes/database/$type/database.inc")) {
+        include_once "./includes/database/database.inc";
+        include_once "./includes/database/$type/database.inc";
+        $type = call_user_func(array("DatabaseConnection_$type", 'driver'));
+      }
+
       // Drupal >=7 requires PDO and drush requires php 5.2, that ships with PDO
       // but it may be compiled with --disable-pdo.
       if (!class_exists('PDO')) {