diff --git a/src/Entity/Index.php b/src/Entity/Index.php
index c642d30..6fc0752 100644
--- a/src/Entity/Index.php
+++ b/src/Entity/Index.php
@@ -294,7 +294,8 @@ class Index extends ConfigEntityBase implements IndexInterface {
     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));
+      $args['@all_datasources'] = implode(', ', array_keys($datasources));
+      throw new SearchApiException(new FormattableMarkup('The datasource with ID "@datasource" could not be retrieved for index %index. The available datasources are: @all_datasources', $args));
     }
     return $datasources[$datasource_id];
   }
@@ -371,6 +372,10 @@ class Index extends ConfigEntityBase implements IndexInterface {
    * {@inheritdoc}
    */
   public function getTrackerInstance() {
+    if ($this->getTrackerSettings() === NULL) {
+      return NULL;
+    }
+
     if (!$this->trackerInstance) {
       if ($this->getTrackerSettings() === array()) {
         $tracker_settings = array(
diff --git a/src/Tests/IntegrationTest.php b/src/Tests/IntegrationTest.php
index c29f378..bf81971 100644
--- a/src/Tests/IntegrationTest.php
+++ b/src/Tests/IntegrationTest.php
@@ -98,6 +98,53 @@ class IntegrationTest extends WebTestBase {
   }
 
   /**
+   * Test what happens when an index has an integer as id/label.
+   *
+   * This needs to be in a seperate index because we also want to see what
+   * happens with the content and we don't want to mess with the content entity
+   * tracking of the other index.
+   */
+  public function testIntegerIndex() {
+    $this->drupalLogin($this->adminUser);
+    $this->getTestServer();
+
+    $this->drupalCreateNode(array('type' => 'article'));
+    $this->drupalCreateNode(array('type' => 'article'));
+
+    $this->drupalGet('admin/config/search/search-api/add-index');
+
+    $this->indexId = 123;
+    $edit = array(
+      'name' => $this->indexId,
+      'id' => $this->indexId,
+      'status' => 1,
+      'description' => 'test Index:: 123~',
+      'server' => 'webtest_server',
+      'datasources[]' => array('entity:node'),
+    );
+    $this->drupalPostForm(NULL, $edit, $this->t('Save'));
+    $this->assertText($this->t('The index was successfully saved.'));
+    $this->assertText($this->t('Successfully tracked @count items for this index.', array('@count' => 2)));
+    $this->assertEqual(2, $this->countTrackedItems());
+
+    $this->enableAllProcessors();
+    $this->checkFieldLabels();
+
+    $this->addFieldsToIndex();
+    $this->removeFieldsFromIndex();
+
+    $this->configureFilter();
+    $this->configureFilterPage();
+    $this->checkProcessorChanges();
+    $this->changeProcessorFieldBoost();
+
+    $this->setReadOnly();
+    $this->disableEnableIndex();
+    $this->changeIndexDatasource();
+    $this->changeIndexServer();
+  }
+
+  /**
    * Tests creating a search server via the UI.
    */
   protected function createServer($server_id = '_test_server') {
diff --git a/src/Tests/Processor/ProcessorTestBase.php b/src/Tests/Processor/ProcessorTestBase.php
index 4032312..abb60e6 100644
--- a/src/Tests/Processor/ProcessorTestBase.php
+++ b/src/Tests/Processor/ProcessorTestBase.php
@@ -87,9 +87,23 @@ abstract class ProcessorTestBase extends EntityUnitTestBase {
       'id' => 'index',
       'name' => 'Index name',
       'status' => TRUE,
-      'datasources' => array('entity:comment', 'entity:node'),
+      'datasource_settings' => array(
+        'entity:comment' => array(
+          'plugin_id' => 'entity:comment',
+          'settings' => array(),
+        ),
+        'entity:node' => array(
+          'plugin_id' => 'entity:node',
+          'settings' => array(),
+        ),
+      ),
       'server' => 'server',
-      'tracker' => 'default',
+      'tracker_settings' => array(
+        'default' => array(
+          'plugin_id' => 'default',
+          'settings' => array()
+        )
+      ),
     ));
     $this->index->setServer($this->server);
     $this->index->setFieldSettings(array(