diff --git a/core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php b/core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php
index e9392b3..4d3ac3d 100644
--- a/core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php
+++ b/core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php
@@ -39,7 +39,7 @@ public function testPostUpdate() {
     $this->assertIdentical($updates, \Drupal::state()->get('post_update_test_execution', []));
 
     $key_value = \Drupal::keyValue('update__post_update');
-    $updates[] = 'block_post_update_disable_blocks_with_missing_contexts';
+    array_unshift($updates, 'block_post_update_disable_blocks_with_missing_contexts');
     $this->assertEqual($updates, $key_value->get('existing_updates'));
   }