diff --git a/core/modules/block_content/block_content.post_update.php b/core/modules/block_content/block_content.post_update.php
index 6b323f99f8..3ad95643bd 100644
--- a/core/modules/block_content/block_content.post_update.php
+++ b/core/modules/block_content/block_content.post_update.php
@@ -8,7 +8,7 @@
 use Drupal\Core\Config\Entity\ConfigEntityUpdater;
 
 /**
- * Adds 'reusable filter to   Custom Block views.
+ * Adds a 'reusable' filter to Custom Block views.
  */
 function block_content_post_update_add_views_reusable_filter(&$sandbox = NULL) {
   $data_table = \Drupal::entityTypeManager()
diff --git a/core/modules/block_content/src/BlockContentAccessControlHandler.php b/core/modules/block_content/src/BlockContentAccessControlHandler.php
index 55bebc03b5..c7138c0238 100644
--- a/core/modules/block_content/src/BlockContentAccessControlHandler.php
+++ b/core/modules/block_content/src/BlockContentAccessControlHandler.php
@@ -2,18 +2,53 @@
 
 namespace Drupal\block_content;
 
+use Drupal\block_content\Event\BlockContentGetDependencyEvent;
 use Drupal\Core\Access\AccessDependentInterface;
 use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Entity\EntityHandlerInterface;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityAccessControlHandler;
+use Drupal\Core\Entity\EntityTypeInterface;
 use Drupal\Core\Session\AccountInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 
 /**
  * Defines the access control handler for the custom block entity type.
  *
  * @see \Drupal\block_content\Entity\BlockContent
  */
-class BlockContentAccessControlHandler extends EntityAccessControlHandler {
+class BlockContentAccessControlHandler extends EntityAccessControlHandler implements EntityHandlerInterface {
+
+  /**
+   * The event dispatcher.
+   *
+   * @var \Symfony\Component\EventDispatcher\EventDispatcherInterface
+   */
+  protected $eventDispatcher;
+
+  /**
+   * BlockContentAccessControlHandler constructor.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
+   *   The entity type.
+   * @param \Symfony\Component\EventDispatcher\EventDispatcherInterface $dispatcher
+   *   The event dispatcher.
+   */
+  public function __construct(EntityTypeInterface $entity_type, EventDispatcherInterface $dispatcher) {
+    parent::__construct($entity_type);
+    $this->eventDispatcher = $dispatcher;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
+    return new static(
+      $entity_type,
+      $container->get('event_dispatcher')
+    );
+  }
 
   /**
    * {@inheritdoc}
@@ -33,9 +68,19 @@ protected function checkAccess(EntityInterface $entity, $operation, AccountInter
       }
       $dependency = $entity->getAccessDependency();
       if (empty($dependency)) {
-        return AccessResult::forbidden("Non-reusable blocks must set an access dependency for access control.");
+        // If an access dependency has not been set let modules set one.
+        $event = new BlockContentGetDependencyEvent($entity);
+        $this->eventDispatcher->dispatch(BlockContentEvents::INLINE_BLOCK_GET_DEPENDENCY, $event);
+        $dependency = $entity->getAccessDependency();
+        if (empty($dependency)) {
+          return AccessResult::forbidden("Non-reusable blocks must set an access dependency for access control.");
+        }
+      }
+      if (empty($dependency->in_preview)) {
+        /** @var \Drupal\Core\Entity\EntityInterface $dependency */
+        $access = $access->andIf($dependency->access($operation, $account, TRUE));
       }
-      $access->andIf($dependency->access($operation, $account, TRUE));
+
     }
     return $access;
   }
diff --git a/core/modules/block_content/src/BlockContentEvents.php b/core/modules/block_content/src/BlockContentEvents.php
new file mode 100644
index 0000000000..865c07aa98
--- /dev/null
+++ b/core/modules/block_content/src/BlockContentEvents.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Drupal\block_content;
+
+/**
+ * Defines events for the block_content module.
+ *
+ * @see \Drupal\block_content\Event\BlockContentGetDependencyEvent
+ */
+final class BlockContentEvents {
+
+  /**
+   * Name of the event when getting the dependency of a non-reusable block.
+   *
+   * This event allows modules to set a dependency of non-reusable block if
+   * \Drupal\Core\Access\AccessDependentTrait::getAccessDependency has not been
+   * called.
+   *
+   * @Event
+   *
+   * @see \Drupal\block_content\Event\BlockContentGetDependencyEvent
+   * @see \Drupal\block_content\BlockContentAccessControlHandler::checkAccess()
+   *
+   * @var string
+   */
+  const INLINE_BLOCK_GET_DEPENDENCY = 'block_content.get_dependency';
+
+}
diff --git a/core/modules/block_content/src/Event/BlockContentGetDependencyEvent.php b/core/modules/block_content/src/Event/BlockContentGetDependencyEvent.php
new file mode 100644
index 0000000000..c0d7a730ac
--- /dev/null
+++ b/core/modules/block_content/src/Event/BlockContentGetDependencyEvent.php
@@ -0,0 +1,47 @@
+<?php
+
+namespace Drupal\block_content\Event;
+
+use Drupal\block_content\BlockContentInterface;
+use Symfony\Component\EventDispatcher\Event;
+
+/**
+ * Block content event to allow setting an access dependency.
+ */
+class BlockContentGetDependencyEvent extends Event {
+
+  /**
+   * The block content entity.
+   *
+   * @var \Drupal\block_content\BlockContentInterface
+   */
+  protected $blockContent;
+
+  /**
+   * The dependency.
+   *
+   * @var \Drupal\Core\Access\AccessibleInterface
+   */
+  protected $dependency;
+
+  /**
+   * BlockContentGetDependencyEvent constructor.
+   *
+   * @param \Drupal\block_content\BlockContentInterface $blockContent
+   *   The block content entity.
+   */
+  public function __construct(BlockContentInterface $blockContent) {
+    $this->blockContent = $blockContent;
+  }
+
+  /**
+   * Gets the block content entity.
+   *
+   * @return \Drupal\block_content\BlockContentInterface
+   *   The block content entity.
+   */
+  public function getBlockContent() {
+    return $this->blockContent;
+  }
+
+}