diff --git a/core/modules/views/lib/Drupal/views/Tests/Handler/HandlerAllTest.php b/core/modules/views/lib/Drupal/views/Tests/Handler/HandlerAllTest.php
index 02fa8f5..2159c04 100644
--- a/core/modules/views/lib/Drupal/views/Tests/Handler/HandlerAllTest.php
+++ b/core/modules/views/lib/Drupal/views/Tests/Handler/HandlerAllTest.php
@@ -95,7 +95,11 @@ public function testHandlers() {
       foreach ($object_types as $type) {
         if (isset($view->{$type})) {
           foreach ($view->{$type} as $handler) {
-            $this->assertTrue($handler instanceof HandlerBase);
+            $this->assertTrue($handler instanceof HandlerBase, format_string(
+              '%handler is an instance of HandlerBase',
+              array(
+                '%handler' => $handler,
+              )));
           }
         }
       }