Index: modules/taxonomy/taxonomy.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/taxonomy/taxonomy.module,v
retrieving revision 1.317
diff -u -p -r1.317 taxonomy.module
--- modules/taxonomy/taxonomy.module	21 Sep 2006 15:31:24 -0000	1.317
+++ modules/taxonomy/taxonomy.module	3 Oct 2006 08:42:20 -0000
@@ -268,6 +268,12 @@ function taxonomy_form_vocabulary($edit 
   return $form;
 }
 
+function taxonomy_form_vocabulary_validate($form_id, $form_values) {
+  if(!array_filter($form_values['nodes'])) {
+    form_set_error('nodes', t('At least one node type is required.'));
+  }
+}
+
 /**
  * Accept the form submission for a vocabulary and save the results.
  */