diff --git a/taxonomy_entity_index.module b/taxonomy_entity_index.module
index 60a2cc2..7ae4d6f 100644
--- a/taxonomy_entity_index.module
+++ b/taxonomy_entity_index.module
@@ -68,7 +68,7 @@ function taxonomy_entity_index_entity_update(EntityInterface $entity) {
   $entity_type_id = $entity->getEntityTypeId();
   $config = \Drupal::config('taxonomy_entity_index.settings');
 
-  $entity_types_to_index = $config->get('types');
+  $entity_types_to_index = $config->get('types') ?: [];
 
   if (!in_array($entity_type_id, $entity_types_to_index)) {
     return;