diff --git a/upgrade.drush.inc b/upgrade.drush.inc
index aed2a8a..2e2b568 100644
--- a/upgrade.drush.inc
+++ b/upgrade.drush.inc
@@ -1794,8 +1794,12 @@ function drush_upgrade_fix_db_url(&$target_alias, $settings_destination) {
     $databases['default']['default']['database'] = $database_name;
     // Handle db prefix
     if (isset($GLOBALS['db_prefix'])) {
-      $append .= "\n\$db_prefix = '" . $GLOBALS['db_prefix'] . "';";
-      $databases['default']['default']['prefix'] = $GLOBALS['db_prefix'];
+	if (! is_array($GLOBALS['db_prefix'])) {
+      	   $append .= "\n\$db_prefix = '" . $GLOBALS['db_prefix'] . "';";
+      	   $databases['default']['default']['prefix'] = $GLOBALS['db_prefix'];
+	} else {
+	   drush_log(dt("db_prefix is set as an array, probably in settings.php site_upgrade expects db_prefix to be a string")); 
+	}
     }
     // Update credentials
     if (isset($target_alias_databases)) {