--- a/testing/web-platform/meta/custom-elements/CustomElementRegistry.html.ini
+++ b/testing/web-platform/meta/custom-elements/CustomElementRegistry.html.ini
@@ -1,10 +1,12 @@
 [CustomElementRegistry.html]
+  prefs: [dom.webcomponents.shadowdom.enabled:true]
   [customElements.define must get callbacks of the constructor prototype]
     expected: FAIL
 
   [customElements.define must get "observedAttributes" property on the constructor prototype when "attributeChangedCallback" is present]
     expected: FAIL
 
   [customElements.define must upgrade elements in the shadow-including tree order]
-    expected: FAIL
-
+    expected:
+      if not stylo: FAIL
+      PASS