diff --git a/core/modules/outside_in/outside_in.module b/core/modules/outside_in/outside_in.module
index 5b9a79a..28f9107 100644
--- a/core/modules/outside_in/outside_in.module
+++ b/core/modules/outside_in/outside_in.module
@@ -55,9 +55,9 @@ function outside_in_block_view_alter(array &$build) {
   $build['#contextual_links']['outside_in'] = [
     'route_parameters' => [],
   ];
-  if (!\Drupal::service('outside_in.manager')->isBlockEditable($build['#plugin_id']) && isset($build['#contextual_links']['block'])) {
+  if (!_outside_in_is_block_editable($build['#plugin_id']) && isset($build['#contextual_links']['block'])) {
     // If this block should not be editable set an attribute which will be used
-    // to remove the link on the client-side.
+    // to remove the link on the client side.
     // The individual links are not available here to remove.
     // @see outside_in.js
     $build['#attributes']['data-outside-in-exclude'] = TRUE;
@@ -103,7 +103,7 @@ function outside_in_preprocess_block(&$variables) {
   $variables['#cache']['contexts'][] = 'outside_in_is_applied';
   /** @var \Drupal\outside_in\OutsideInManagerInterface $outside_in_manager */
   $outside_in_manager = \Drupal::service('outside_in.manager');
-  if ($outside_in_manager->isBlockEditable($variables['plugin_id']) && $outside_in_manager->isApplicable()) {
+  if (_outside_in_is_block_editable($variables['plugin_id']) && $outside_in_manager->isApplicable()) {
     // Add class and attributes to all blocks to allow Javascript to target.
     $variables['attributes']['class'][] = 'outside-in-editable';
     $variables['attributes']['data-drupal-outsidein'] = 'editable';
@@ -164,3 +164,18 @@ function outside_in_css_alter(&$css, AttachedAssetsInterface $assets) {
     $css[$path]['group'] = 200;
   }
 }
+
+/**
+ * Checks whether a block is editable by this module.
+ *
+ * @param string $plugin_id
+ *   The plugin ID for the block to check.
+ *
+ * @return bool
+ *   TRUE if the block should have the "Quick Edit" link provided by this
+ *   module.
+ */
+function _outside_in_is_block_editable($plugin_id) {
+  $non_editable_blocks = ['page_title_block', 'system_main_block'];
+  return !in_array($plugin_id, $non_editable_blocks, TRUE);
+}
diff --git a/core/modules/outside_in/src/OutsideInManager.php b/core/modules/outside_in/src/OutsideInManager.php
index 26bda75..666a938 100644
--- a/core/modules/outside_in/src/OutsideInManager.php
+++ b/core/modules/outside_in/src/OutsideInManager.php
@@ -63,12 +63,4 @@ public function isApplicable() {
     return $this->account->hasPermission('administer blocks') && !$is_admin_route && !$is_admin_demo_route;
   }
 
-  /**
-   * {@inheritdoc}
-   */
-  public function isBlockEditable($plugin_id) {
-    $non_editable_blocks = ['page_title_block', 'system_main_block'];
-    return !in_array($plugin_id, $non_editable_blocks, TRUE);
-  }
-
 }
diff --git a/core/modules/outside_in/src/OutsideInManagerInterface.php b/core/modules/outside_in/src/OutsideInManagerInterface.php
index 054074e..684adb3 100644
--- a/core/modules/outside_in/src/OutsideInManagerInterface.php
+++ b/core/modules/outside_in/src/OutsideInManagerInterface.php
@@ -15,16 +15,4 @@
    */
   public function isApplicable();
 
-  /**
-   * Checks whether a block is editable by this module.
-   *
-   * @param string $plugin_id
-   *   The plugin ID for the block to check.
-   *
-   * @return bool
-   *   TRUE if the block should have the "Quick Edit" link provided by this
-   *   module.
-   */
-  public function isBlockEditable($plugin_id);
-
 }