diff --git a/src/Entity/Index.php b/src/Entity/Index.php
index 614e0fe..179206b 100644
--- a/src/Entity/Index.php
+++ b/src/Entity/Index.php
@@ -18,6 +18,7 @@ use Drupal\search_api\Query\QueryInterface;
 use Drupal\search_api\Query\ResultSetInterface;
 use Drupal\search_api\SearchApiException;
 use Drupal\search_api\ServerInterface;
+use Drupal\search_api\Tracker\TrackerInterface;
 use Drupal\search_api\Utility;
 use Drupal\user\TempStoreException;
 use Drupal\views\Views;
@@ -306,11 +307,13 @@ class Index extends ConfigEntityBase implements IndexInterface {
    */
   public function getDatasource($datasource_id) {
     $datasources = $this->getDatasources();
+
     if (empty($datasources[$datasource_id])) {
       $args['@datasource'] = $datasource_id;
       $args['%index'] = $this->label();
       throw new SearchApiException(new FormattableMarkup('The datasource with ID "@datasource" could not be retrieved for index %index.', $args));
     }
+
     return $datasources[$datasource_id];
   }
 
@@ -358,12 +361,7 @@ class Index extends ConfigEntityBase implements IndexInterface {
    * {@inheritdoc}
    */
   public function getTrackerId() {
-    if (is_null($this->tracker_settings)) {
-      return 'default';
-    }
-
-    $plugins = array_keys($this->tracker_settings);
-    return $this->tracker_settings[$plugins[0]]['plugin_id'];
+    return $this->getTrackerInstance()->getPluginId();
   }
 
   /**
@@ -374,12 +372,15 @@ class Index extends ConfigEntityBase implements IndexInterface {
 
       if (is_null($this->tracker_settings)) {
         $tracker_plugin_configuration = array('index' => $this);
-      } else {
+        $plugin_id = 'default';
+      }
+      else {
         $plugins = array_keys($this->tracker_settings);
         $tracker_plugin_configuration = array('index' => $this) + $this->tracker_settings[$plugins[0]]['settings'];
+        $plugin_id = $this->tracker_settings[$plugins[0]]['plugin_id'];
       }
 
-      if (!($this->trackerInstance = \Drupal::service('plugin.manager.search_api.tracker')->createInstance($this->getTrackerId(), $tracker_plugin_configuration))) {
+      if (!($this->trackerInstance = \Drupal::service('plugin.manager.search_api.tracker')->createInstance($plugin_id, $tracker_plugin_configuration))) {
         $args['@tracker'] = $this->getTrackerId();
         $args['%index'] = $this->label();
         throw new SearchApiException(new FormattableMarkup('The tracker with ID "@tracker" could not be retrieved for index %index.', $args));
@@ -392,6 +393,15 @@ class Index extends ConfigEntityBase implements IndexInterface {
   /**
    * {@inheritdoc}
    */
+  public function setTracker(TrackerInterface $tracker) {
+    $this->trackerInstance = $tracker;
+
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function hasValidServer() {
     return $this->server !== NULL && Server::load($this->server) !== NULL;
   }
@@ -1003,6 +1013,14 @@ class Index extends ConfigEntityBase implements IndexInterface {
       }
     }
 
+    // Add tracker settings.
+    $this->tracker_settings = array(
+      $this->getTrackerId() => array(
+        'plugin_id' => $this->getTrackerId(),
+        'settings' => $this->getTrackerInstance()->getConfiguration(),
+      )
+    );
+
     // Call the preIndexSave() method of all applicable processors.
     foreach ($this->getProcessorsByStage(ProcessorInterface::STAGE_PRE_INDEX_SAVE) as $processor) {
       $processor->preIndexSave();
diff --git a/src/Form/IndexForm.php b/src/Form/IndexForm.php
index 1db8781..a415956 100644
--- a/src/Form/IndexForm.php
+++ b/src/Form/IndexForm.php
@@ -554,12 +554,7 @@ class IndexForm extends EntityForm {
 
     $tracker_form_state = new SubFormState($form_state, array('tracker_config'));
     $tracker->submitConfigurationForm($form['tracker_config'], $tracker_form_state);
-    $index->set('tracker_settings', array(
-      $tracker_id => array(
-        'plugin_id' => $tracker_id,
-        'settings' => $tracker->getConfiguration(),
-      )
-    ));
+    $index->setTracker($tracker);
   }
 
   /**
diff --git a/src/IndexInterface.php b/src/IndexInterface.php
index 85570ae..98633d1 100644
--- a/src/IndexInterface.php
+++ b/src/IndexInterface.php
@@ -8,10 +8,12 @@
 namespace Drupal\search_api;
 
 use Drupal\Core\Config\Entity\ConfigEntityInterface;
+use Drupal\search_api\Datasource\DatasourceInterface;
 use Drupal\search_api\Item\FieldInterface;
 use Drupal\search_api\Processor\ProcessorInterface;
 use Drupal\search_api\Query\QueryInterface;
 use Drupal\search_api\Query\ResultSetInterface;
+use Drupal\search_api\Tracker\TrackerInterface;
 
 /**
  * Defines the interface for index entities.
@@ -204,6 +206,16 @@ interface IndexInterface extends ConfigEntityInterface {
   public function getTrackerInstance();
 
   /**
+   * Sets the tracker the index uses.
+   *
+   * @param \Drupal\search_api\Tracker\TrackerInterface $tracker
+   *   The tracker the index uses.
+   *
+   * @return $this
+   */
+  public function setTracker(TrackerInterface $tracker);
+
+  /**
    * Determines whether this index is lying on a valid server.
    *
    * @return bool
diff --git a/tests/src/Kernel/DependencyRemovalTest.php b/tests/src/Kernel/DependencyRemovalTest.php
index 08a16e7..2619ae5 100644
--- a/tests/src/Kernel/DependencyRemovalTest.php
+++ b/tests/src/Kernel/DependencyRemovalTest.php
@@ -122,7 +122,7 @@ class DependencyRemovalTest extends KernelTestBase {
     // Set the server on the index and save that, too. However, we don't want
     // the index enabled, since that would lead to all kinds of overhead which
     // is completely irrelevant for this test.
-    $this->index->set('server', $server->id());
+    $this->index->setServer($server);
     $this->index->disable();
     $this->index->save();
 
@@ -348,16 +348,15 @@ class DependencyRemovalTest extends KernelTestBase {
     // server.
     $dependency_key = $this->dependency->getConfigDependencyKey();
     $dependency_name = $this->dependency->getConfigDependencyName();
-    $this->index->set('tracker_settings', array(
-      'search_api_test_dependencies' => array(
-        'plugin_id' => 'search_api_test_dependencies',
-        'settings' => array(
-          $dependency_key => array(
-            $dependency_name,
-          ),
-        )
-      )
-    ));
+
+    $tracker = \Drupal::getContainer()
+      ->get('plugin.manager.search_api.tracker')
+      ->createInstance('search_api_test_dependencies', array(
+        $dependency_key => array(
+          $dependency_name,
+        ),
+      ));
+    $this->index->setTracker($tracker);
     $this->index->save();
 
     // Check the dependencies were calculated correctly.
@@ -391,10 +390,9 @@ class DependencyRemovalTest extends KernelTestBase {
 
     // Depending on whether the plugin should have removed the dependency or
     // not, make sure the right action was taken.
-    $config = $this->index->get('tracker_settings');
-    $plugins = array_keys($config);
-    $tracker = $config[$plugins[0]]['plugin_id'];
-    $tracker_config = $config[$plugins[0]]['settings'];
+    $tracker_instance = $this->index->getTrackerInstance();
+    $tracker = $tracker_instance->getPluginId();
+    $tracker_config = $tracker_instance->getConfiguration();
     if ($remove_dependency) {
       $this->assertEquals('search_api_test_dependencies', $tracker, 'Tracker not reset');
       $this->assertEmpty($tracker_config, 'Tracker settings adapted');
@@ -426,7 +424,10 @@ class DependencyRemovalTest extends KernelTestBase {
         'settings' => array(),
       ),
     ));
-    $this->index->set('tracker', 'search_api_test_dependencies');
+    $tracker = \Drupal::getContainer()
+      ->get('plugin.manager.search_api.tracker')
+      ->createInstance('search_api_test_dependencies');
+    $this->index->setTracker($tracker);
     $this->index->save();
 
     // Check the dependencies were calculated correctly.