diff -u b/core/modules/taxonomy/taxonomy.admin.inc b/core/modules/taxonomy/taxonomy.admin.inc
--- b/core/modules/taxonomy/taxonomy.admin.inc
+++ b/core/modules/taxonomy/taxonomy.admin.inc
@@ -240,7 +240,7 @@
     ),
   );
   foreach ($current_page as $key => $term) {
-    $form[$key]['#term'] = $term;
+    $form['terms'][$key]['#term'] = $term;
     $form['terms'][$key]['term'] = array(
       '#prefix' => isset($term->depth->value) && $term->depth->value > 0 ? theme('indentation', array('size' => $term->depth->value)) : '',
       '#type' => 'link',
@@ -427,8 +427,8 @@
       $term = $form['terms'][$tid]['#term'];
       // Give terms at the root level a weight in sequence with terms on previous pages.
       if ($values['term']['parent'] == 0 && $term->weight->value != $weight) {
-        $term['weight'] = $weight;
-        $changed_terms[$term['tid']] = $term;
+        $term->weight->value = $weight;
+        $changed_terms[$term->id()] = $term;
       }
       // Terms not at the root level can safely start from 0 because they're all on this page.
       elseif ($values['term']['parent'] > 0) {