diff --git a/test/unit/styling-scoped.html b/test/unit/styling-scoped.html
index ae9d81b95f..d3a429006b 100644
--- a/test/unit/styling-scoped.html
+++ b/test/unit/styling-scoped.html
@@ -1166,9 +1166,9 @@
       el.shadowRoot.appendChild(div);
       flush();
       div.className = 'foo';
-      assert.isTrue(div.classList.contains('foo'));
-      assert.isTrue(div.classList.contains('style-scope'));
-      assert.isTrue(div.classList.contains('x-scope-class'));
+      assert.isTrue(div.classList.contains('foo'), 'foo should be in classList');
+      assert.isTrue(div.classList.contains('style-scope'), 'style-scope should be in classList');
+      assert.isTrue(div.classList.contains('x-scope-class'), 'x-scope-class should be in classList');
       el.shadowRoot.appendChild(div);
       flush();
       document.body.removeChild(el);