diff --git a/src/Entity/Index.php b/src/Entity/Index.php
index e2a98d4..644c26d 100644
--- a/src/Entity/Index.php
+++ b/src/Entity/Index.php
@@ -153,12 +153,7 @@ class Index extends ConfigEntityBase implements IndexInterface {
    *
    * @var array
    */
-  protected $tracker_settings = array(
-    'default' => array(
-      'plugin_id' => 'default',
-      'settings' => array()
-    ),
-  );
+  protected $tracker_settings = NULL;
 
   /**
    * The tracker plugin instance.
@@ -361,7 +356,8 @@ class Index extends ConfigEntityBase implements IndexInterface {
    * {@inheritdoc}
    */
   public function hasValidTracker() {
-    return (bool) \Drupal::service('plugin.manager.search_api.tracker')->getDefinition($this->getTrackerId(), FALSE);
+    return (bool) \Drupal::service('plugin.manager.search_api.tracker')
+      ->getDefinition($this->getTrackerId(), FALSE);
   }
 
   /**
@@ -631,7 +627,7 @@ class Index extends ConfigEntityBase implements IndexInterface {
     }
     if (isset($this->getFields()[$new_field_id])) {
       $args['%field_id'] = $new_field_id;
-      throw new SearchApiException(new FormattableMarkup('%field_id already exists and can\'t be used as a new field id.', $args));
+      throw new SearchApiException(new FormattableMarkup("%field_id already exists and can't be used as a new field id.", $args));
     }
 
     $this->fieldInstances[$new_field_id] = $this->fieldInstances[$old_field_id];
@@ -1009,19 +1005,6 @@ class Index extends ConfigEntityBase implements IndexInterface {
       $this->disable();
     }
 
-    $this->field_settings = array();
-    foreach ($this->getFields() as $field_id => $field) {
-      $this->field_settings[$field_id] = $field->getSettings();
-    }
-
-    // Remove all "locked" and "hidden" flags from all fields of the index. If
-    // they are still valid, they should be re-added by the processors.
-    foreach ($this->field_settings as $field_id => $field_settings) {
-      unset($this->field_settings[$field_id]['indexed_locked']);
-      unset($this->field_settings[$field_id]['type_locked']);
-      unset($this->field_settings[$field_id]['hidden']);
-    }
-
     // We first have to check for locked processors, otherwise their
     // preIndexSave() methods might not be called in the next step.
     $this->processor_settings = array();
diff --git a/src/Item/Field.php b/src/Item/Field.php
index 2d14eb4..8580c59 100644
--- a/src/Item/Field.php
+++ b/src/Item/Field.php
@@ -167,7 +167,7 @@ class Field implements \IteratorAggregate, FieldInterface {
    * {@inheritdoc}
    */
   public function setIndex(IndexInterface $index) {
-    if ($this->index instanceof IndexInterface && $this->index->id() != $index->id()) {
+    if ($this->index->id() != $index->id()) {
       throw new \InvalidArgumentException('Attempted to change the index of a field object.');
     }
     $this->index = $index;