diff --git a/core/modules/search/src/Form/SearchBlockForm.php b/core/modules/search/src/Form/SearchBlockForm.php
index 4edcd73..f3a7a8c 100644
--- a/core/modules/search/src/Form/SearchBlockForm.php
+++ b/core/modules/search/src/Form/SearchBlockForm.php
@@ -77,6 +77,7 @@ public function getFormId() {
    */
   public function buildForm(array $form, FormStateInterface $form_state, $entity_id = NULL) {
     // Set up the form to submit using GET to the correct search page.
+    // But first, make sure this search page is active.
     if (!$entity_id) {
       $entity_id = $this->searchPageRepository->getDefaultSearchPage();
       // SearchPageRepository::getDefaultSearchPage() depends on
@@ -87,7 +88,12 @@ public function buildForm(array $form, FormStateInterface $form_state, $entity_i
       $this->renderer->addCacheableDependency($form, $this->configFactory->get('search.settings'));
     }
 
-    if (!$entity_id) {
+    if ($entity_id) {
+      $pages = $this->searchPageRepository->getActiveSearchPages();
+      $entity = $pages[$entity_id] ?? NULL;
+    }
+
+    if (!isset($entity)) {
       $form['message'] = [
         '#markup' => $this->t('Search is currently disabled'),
       ];
diff --git a/core/modules/search/src/SearchPageRepositoryInterface.php b/core/modules/search/src/SearchPageRepositoryInterface.php
index 6169fbc..7ed5d43 100644
--- a/core/modules/search/src/SearchPageRepositoryInterface.php
+++ b/core/modules/search/src/SearchPageRepositoryInterface.php
@@ -34,8 +34,8 @@ public function getIndexableSearchPages();
   /**
    * Returns the default search page.
    *
-   * @return \Drupal\search\SearchPageInterface|bool
-   *   The search page entity, or FALSE if no pages are active.
+   * @return string|false
+   *   The default search page entity ID, or FALSE if no pages are active.
    */
   public function getDefaultSearchPage();