diff --git a/core/modules/block/lib/Drupal/block/Controller/CategoryAutocompleteController.php b/core/modules/block/lib/Drupal/block/Controller/CategoryAutocompleteController.php
index 1b611471c043cca89d14084a6fbd357975843451..0c35e82c051b40c81f893263f4c3c1f8aac16fca 100644
--- a/core/modules/block/lib/Drupal/block/Controller/CategoryAutocompleteController.php
+++ b/core/modules/block/lib/Drupal/block/Controller/CategoryAutocompleteController.php
@@ -59,7 +59,7 @@ public function autocomplete(Request $request) {
     $matches = array();
     foreach ($this->blockManager->getCategories() as $category) {
       if (stripos($category, $typed_category) === 0) {
-        $matches[$category] = String::checkPlain($category);
+        $matches[] = array('value' => $category, 'label' => String::checkPlain($category));
       }
     }
     return new JsonResponse($matches);
diff --git a/core/modules/block/tests/Drupal/block/Tests/CategoryAutocompleteTest.php b/core/modules/block/tests/Drupal/block/Tests/CategoryAutocompleteTest.php
index 29d75d0ff8fc039bc5f8dfeab5ef59eb747ad6e4..26bd6b9151da83b07b7a510323bb914c06dd3acd 100644
--- a/core/modules/block/tests/Drupal/block/Tests/CategoryAutocompleteTest.php
+++ b/core/modules/block/tests/Drupal/block/Tests/CategoryAutocompleteTest.php
@@ -59,8 +59,8 @@ public function setUp() {
    */
   public function testAutocompleteSuggestions($string, $suggestions) {
     $suggestions = array_map(function ($suggestion) {
-      return String::checkPlain($suggestion);
-    }, array_combine($suggestions, $suggestions));
+      return array('value' => $suggestion, 'label' => String::checkPlain($suggestion));
+    }, $suggestions);
     $result = $this->autocompleteController->autocomplete(new Request(array('q' => $string)));
     $this->assertSame($suggestions, json_decode($result->getContent(), TRUE));
   }