diff --git a/modules/taxonomy/taxonomy.module b/modules/taxonomy/taxonomy.module
index f170430..d9ff16c 100644
--- a/modules/taxonomy/taxonomy.module
+++ b/modules/taxonomy/taxonomy.module
@@ -1204,6 +1204,8 @@ function taxonomy_implode_tags($tags, $vid = NULL) {
  *   - parent: a term ID of a term whose children are allowed. This should be
  *     '0' if all terms in a vocabulary are allowed. The allowed values do not
  *     include the parent term.
+ * - allow_term_autocreation: a boolean indicating whether or not unknown
+ *   values will be converted to new terms in the vocabulary
  *
  */
 function taxonomy_field_info() {
@@ -1220,6 +1222,7 @@ function taxonomy_field_info() {
             'parent' => '0',
           ),
         ),
+        'allow_term_autocreation' => TRUE,
       ),
     ),
   );
@@ -1520,7 +1523,7 @@ function taxonomy_autocomplete_validate($element, &$form_state) {
       if ($possibilities = taxonomy_term_load_multiple(array(), array('name' => trim($typed_term), 'vid' => array_keys($vocabularies)))) {
         $term = array_pop($possibilities);
       }
-      else {
+      else if (!isset($field['settings']['allow_term_autocreation']) || $field['settings']['allow_term_autocreation']) {
         $vocabulary = reset($vocabularies);
         $term = array(
           'tid' => 'autocreate',
@@ -1529,7 +1532,14 @@ function taxonomy_autocomplete_validate($element, &$form_state) {
           'vocabulary_machine_name' => $vocabulary->machine_name,
         );
       }
-      $value[] = (array)$term;
+      else {
+        $term = NULL;
+        form_error($element, t('%name: illegal value: %value.', array('%name' => t($element['#title']), '%value' => $typed_term)));
+      }
+
+      if (isset($term)) {
+        $value[] = (array)$term;
+      }
     }
   }
 
@@ -1572,6 +1582,13 @@ function taxonomy_field_settings_form($field, $instance, $has_data) {
     );
   }
 
+  $form['allow_term_autocreation'] = array(
+    '#type' => 'checkbox',
+    '#title' => t('Allow autocreation of new terms'),
+    '#default_value' => (!isset($field['settings']['allow_term_autocreation']) || $field['settings']['allow_term_autocreation']) ? TRUE : FALSE,
+    '#description' => t('When enabled, new terms are automatically created for unknown values.'),
+  );
+
   return $form;
 }