diff --git taxonomy_export.inc.old taxonomy_export.inc
index 770537a..eb0bca8 100644
--- taxonomy_export.inc.old
+++ taxonomy_export.inc
@@ -66,7 +66,7 @@ function taxonomy_export_set_machine_name(&$vocabulary) {
   }
   // Else, attempt to generate a new machine name
   else {
-    if (!$vocabulary->machine_name) {
+    if (!isset($vocabulary->machine_name) || !$vocabulary->machine_name) {
       $vocabulary->machine_name = _taxonomy_export_generate_machine_name($vocabulary->name);
     }