diff --git modules/forum/forum.install modules/forum/forum.install
index a5dbc3e..f297ac1 100644
--- modules/forum/forum.install
+++ modules/forum/forum.install
@@ -45,7 +45,7 @@ function forum_enable() {
   }
 
   // Create the 'taxonomy_forums' field if it doesn't already exist.
-  if (!field_info_field('taxonomy_forums')) {
+  if (!field_info_field('taxonomy_' . $vocabulary->machine_name)) {
     $field = array(
       'field_name' => 'taxonomy_' . $vocabulary->machine_name,
       'type' => 'taxonomy_term_reference',
diff --git modules/forum/forum.module modules/forum/forum.module
index 8388cda..feb63a3 100644
--- modules/forum/forum.module
+++ modules/forum/forum.module
@@ -255,8 +255,11 @@ function forum_uri($forum) {
  *   Boolean indicating if the node can be assigned to a forum.
  */
 function _forum_node_check_node_type($node) {
+  $vid = variable_get('forum_nav_vocabulary', 0);
+  $vocabulary = taxonomy_vocabulary_load($vid);
+
   // Fetch information about the forum field.
-  $field = field_info_instance('node', 'taxonomy_forums', $node->type);
+  $field = field_info_instance('node', 'taxonomy_' . $vocabulary->machine_name, $node->type);
 
   return is_array($field);
 }