diff --git a/autosave.module b/autosave.module
index 03be427..3853337 100644
--- a/autosave.module
+++ b/autosave.module
@@ -288,6 +288,22 @@ function autosave_restore($form_id, $timestamp) {
   if ($record) {
     $form_state = unserialize($record->serialized);
 
+    // Manually load include files that the form depends on. Normally this will
+    // be handled automatically by form_get_cache() (which this code is copied
+    // from) but if the autosaved data is old enough that the cache_form entry
+    // is no longer present, it needs to be done manually.
+    if (!empty($form_state['build_info']['files'])) {
+      foreach ($form_state['build_info']['files'] as $file) {
+        if (is_array($file)) {
+          $file += array('type' => 'inc', 'name' => $file['module']);
+          module_load_include($file['type'], $file['module'], $file['name']);
+        }
+        elseif (file_exists($file)) {
+          require_once DRUPAL_ROOT . '/' . $file;
+       }
+      }
+    }
+
     // Disable the "this form has already been submitted" nonsense by making
     // Drupal think the form is being rebuilt as part of a multi-step form.
     $form_state['rebuild'] = TRUE;