Index: wp-admin/includes/update-core.php
===================================================================
--- wp-admin/includes/update-core.php	(revision 19063)
+++ wp-admin/includes/update-core.php	(working copy)
@@ -337,7 +337,7 @@
 	$required_mysql_version = '5.0';
 	$wp_version = '3.3';
 	$php_compat     = version_compare( $php_version, $required_php_version, '>=' );
-	if ( file_exists( WP_CONTENT_DIR . '/db.php' ) && empty( $this->is_mysql ) )
+	if ( file_exists( WP_CONTENT_DIR . '/db.php' ) && empty( $wpdb->is_mysql ) )
 		$mysql_compat = true;
 	else
 		$mysql_compat = version_compare( $mysql_version, $required_mysql_version, '>=' );