diff --git a/pathauto.api.php b/pathauto.api.php
index 4af9023..03382d8 100644
--- a/pathauto.api.php
+++ b/pathauto.api.php
@@ -109,7 +109,7 @@ function hook_pathauto_is_alias_reserved($alias, $source, $langcode) {
 function hook_pathauto_pattern_alter(&$pattern, array $context) {
   // Switch out any [node:created:*] tokens with [node:updated:*] on update.
   if ($context['module'] == 'node' && ($context['op'] == 'update')) {
-    $pattern = preg_replace('/\[node:created(\:[^]]*)?\]/', '[node:updated$1]', $pattern);
+    $pattern->setPattern(preg_replace('/\[node:created(\:[^]]*)?\]/', '[node:updated$1]', $pattern->getPattern()));
   }
 }