diff --git a/core/tests/Drupal/KernelTests/Core/Theme/StableTemplateOverrideTest.php b/core/tests/Drupal/KernelTests/Core/Theme/StableTemplateOverrideTest.php
index f6e6cd4..69d9e8c 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/StableTemplateOverrideTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/StableTemplateOverrideTest.php
@@ -100,7 +100,7 @@ public function testStableTemplateOverrides() {
           continue;
         }
 
-        $this->assertEquals('core/themes/stable', $info['theme path'], $info['template'] . ' overridden in Stable.');
+        $this->assertEquals('core/themes/stable', $info['theme path'], $info['template'] . '.html.twig overridden in Stable.');
       }
     }
   }