diff --git a/vagrant.drush.inc b/vagrant.drush.inc
index 33ad804..c56ff0b 100644
--- a/vagrant.drush.inc
+++ b/vagrant.drush.inc
@@ -36,7 +36,7 @@ function vagrant_drush_init() {
     $cache = drush_cache_get_multiple($cache_ids, 'vagrant');
 
     // Check if Vagrant is installed
-    if (!isset($cache['vagrant_path'])) {
+    if (!isset($cache['vagrant_path']) || !isset($cache['vagrant_path']->data)) {
       $vagrant_path = drush_shell_exec_output(drush_shell_exec('which vagrant'));
       drush_cache_set('vagrant_path', $vagrant_path[0], 'vagrant', DRUSH_CACHE_TEMPORARY);
     }