Index: phone.module
===================================================================
--- phone.module	(revision 185)
+++ phone.module	(revision 186)
@@ -461,6 +461,7 @@
 function phone_field_presave($entity_type, $entity, $field, $instance, $langcode, &$items) {
   // Load libphonenumber.
   phone_libphonenumber();
+  module_load_include('inc', 'phone', 'phone.libphonenumber');
 
   foreach ($items as $delta => $item) {
     $extension = isset($item['extension']) ? trim($item['extension']) : '';