diff --git a/dom/html/nsHTMLContentSink.cpp b/dom/html/nsHTMLContentSink.cpp
index 6e808f87e8..bba5d38ab2 100644
--- a/dom/html/nsHTMLContentSink.cpp
+++ b/dom/html/nsHTMLContentSink.cpp
@@ -265,7 +265,8 @@ NS_NewHTMLElement(Element** aResult, already_AddRefed<mozilla::dom::NodeInfo>&&
     return NS_ERROR_OUT_OF_MEMORY;
   }
 
-  if (isCustomElementName || aIs) {
+  if (CustomElementRegistry::IsCustomElementEnabled() &&
+      (isCustomElementName || aIs)) {
     nsContentUtils::SetupCustomElement(*aResult, aIs);
   }