diff -u b/core/lib/Drupal/Core/Entity/EntityTypeBundleInfoInterface.php b/core/lib/Drupal/Core/Entity/EntityTypeBundleInfoInterface.php
--- b/core/lib/Drupal/Core/Entity/EntityTypeBundleInfoInterface.php
+++ b/core/lib/Drupal/Core/Entity/EntityTypeBundleInfoInterface.php
@@ -26,7 +26,7 @@
    * @param string $entity_type_id
    *   The entity type ID.
    *
-   * @return mixed[]
+   * @return array[]
    *   An array of bundle information whose keys are bundle names and values
    *   are (second-level) arrays with the following keys:
    *   - label: The human-readable name of the bundle.