diff --git a/Libraries/LibWeb/DOM/ElementFactory.cpp b/Libraries/LibWeb/DOM/ElementFactory.cpp
index ad0db96c870..cdb07303a80 100644
--- a/Libraries/LibWeb/DOM/ElementFactory.cpp
+++ b/Libraries/LibWeb/DOM/ElementFactory.cpp
@@ -545,6 +545,7 @@ WebIDL::ExceptionOr<GC::Ref<Element>> create_element(Document& document, FlyStri
         //    namespace prefix set to prefix, local name set to localName, custom element state set to "undefined", custom element definition set to null,
         //    is value set to is, and node document set to document.
         auto element = create_html_element(realm, document, QualifiedName { local_name, prefix, Namespace::HTML });
+        element->set_is_value(is_value);
 
         // 3. If the synchronous custom elements flag is set, then run this step while catching any exceptions:
         if (synchronous_custom_elements_flag) {
diff --git a/Tests/LibWeb/Text/expected/wpt-import/custom-elements/builtin-coverage.txt b/Tests/LibWeb/Text/expected/wpt-import/custom-elements/builtin-coverage.txt
new file mode 100644
index 00000000000..194f4aa78f2
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/custom-elements/builtin-coverage.txt
@@ -0,0 +1,449 @@
+Harness status: OK
+
+Found 444 tests
+
+444 Pass
+Pass	a: Define a customized built-in element
+Pass	a: Operator 'new' should instantiate a customized built-in element
+Pass	a: document.createElement() should instantiate a customized built-in element
+Pass	a: innerHTML should instantiate a customized built-in element
+Pass	abbr: Define a customized built-in element
+Pass	abbr: Operator 'new' should instantiate a customized built-in element
+Pass	abbr: document.createElement() should instantiate a customized built-in element
+Pass	abbr: innerHTML should instantiate a customized built-in element
+Pass	address: Define a customized built-in element
+Pass	address: Operator 'new' should instantiate a customized built-in element
+Pass	address: document.createElement() should instantiate a customized built-in element
+Pass	address: innerHTML should instantiate a customized built-in element
+Pass	area: Define a customized built-in element
+Pass	area: Operator 'new' should instantiate a customized built-in element
+Pass	area: document.createElement() should instantiate a customized built-in element
+Pass	area: innerHTML should instantiate a customized built-in element
+Pass	article: Define a customized built-in element
+Pass	article: Operator 'new' should instantiate a customized built-in element
+Pass	article: document.createElement() should instantiate a customized built-in element
+Pass	article: innerHTML should instantiate a customized built-in element
+Pass	aside: Define a customized built-in element
+Pass	aside: Operator 'new' should instantiate a customized built-in element
+Pass	aside: document.createElement() should instantiate a customized built-in element
+Pass	aside: innerHTML should instantiate a customized built-in element
+Pass	audio: Define a customized built-in element
+Pass	audio: Operator 'new' should instantiate a customized built-in element
+Pass	audio: document.createElement() should instantiate a customized built-in element
+Pass	audio: innerHTML should instantiate a customized built-in element
+Pass	b: Define a customized built-in element
+Pass	b: Operator 'new' should instantiate a customized built-in element
+Pass	b: document.createElement() should instantiate a customized built-in element
+Pass	b: innerHTML should instantiate a customized built-in element
+Pass	base: Define a customized built-in element
+Pass	base: Operator 'new' should instantiate a customized built-in element
+Pass	base: document.createElement() should instantiate a customized built-in element
+Pass	base: innerHTML should instantiate a customized built-in element
+Pass	bdi: Define a customized built-in element
+Pass	bdi: Operator 'new' should instantiate a customized built-in element
+Pass	bdi: document.createElement() should instantiate a customized built-in element
+Pass	bdi: innerHTML should instantiate a customized built-in element
+Pass	bdo: Define a customized built-in element
+Pass	bdo: Operator 'new' should instantiate a customized built-in element
+Pass	bdo: document.createElement() should instantiate a customized built-in element
+Pass	bdo: innerHTML should instantiate a customized built-in element
+Pass	blockquote: Define a customized built-in element
+Pass	blockquote: Operator 'new' should instantiate a customized built-in element
+Pass	blockquote: document.createElement() should instantiate a customized built-in element
+Pass	blockquote: innerHTML should instantiate a customized built-in element
+Pass	body: Define a customized built-in element
+Pass	body: Operator 'new' should instantiate a customized built-in element
+Pass	body: document.createElement() should instantiate a customized built-in element
+Pass	body: document parser should instantiate a customized built-in element
+Pass	br: Define a customized built-in element
+Pass	br: Operator 'new' should instantiate a customized built-in element
+Pass	br: document.createElement() should instantiate a customized built-in element
+Pass	br: innerHTML should instantiate a customized built-in element
+Pass	button: Define a customized built-in element
+Pass	button: Operator 'new' should instantiate a customized built-in element
+Pass	button: document.createElement() should instantiate a customized built-in element
+Pass	button: innerHTML should instantiate a customized built-in element
+Pass	canvas: Define a customized built-in element
+Pass	canvas: Operator 'new' should instantiate a customized built-in element
+Pass	canvas: document.createElement() should instantiate a customized built-in element
+Pass	canvas: innerHTML should instantiate a customized built-in element
+Pass	caption: Define a customized built-in element
+Pass	caption: Operator 'new' should instantiate a customized built-in element
+Pass	caption: document.createElement() should instantiate a customized built-in element
+Pass	caption: innerHTML should instantiate a customized built-in element
+Pass	cite: Define a customized built-in element
+Pass	cite: Operator 'new' should instantiate a customized built-in element
+Pass	cite: document.createElement() should instantiate a customized built-in element
+Pass	cite: innerHTML should instantiate a customized built-in element
+Pass	code: Define a customized built-in element
+Pass	code: Operator 'new' should instantiate a customized built-in element
+Pass	code: document.createElement() should instantiate a customized built-in element
+Pass	code: innerHTML should instantiate a customized built-in element
+Pass	col: Define a customized built-in element
+Pass	col: Operator 'new' should instantiate a customized built-in element
+Pass	col: document.createElement() should instantiate a customized built-in element
+Pass	col: innerHTML should instantiate a customized built-in element
+Pass	colgroup: Define a customized built-in element
+Pass	colgroup: Operator 'new' should instantiate a customized built-in element
+Pass	colgroup: document.createElement() should instantiate a customized built-in element
+Pass	colgroup: innerHTML should instantiate a customized built-in element
+Pass	data: Define a customized built-in element
+Pass	data: Operator 'new' should instantiate a customized built-in element
+Pass	data: document.createElement() should instantiate a customized built-in element
+Pass	data: innerHTML should instantiate a customized built-in element
+Pass	dd: Define a customized built-in element
+Pass	dd: Operator 'new' should instantiate a customized built-in element
+Pass	dd: document.createElement() should instantiate a customized built-in element
+Pass	dd: innerHTML should instantiate a customized built-in element
+Pass	del: Define a customized built-in element
+Pass	del: Operator 'new' should instantiate a customized built-in element
+Pass	del: document.createElement() should instantiate a customized built-in element
+Pass	del: innerHTML should instantiate a customized built-in element
+Pass	details: Define a customized built-in element
+Pass	details: Operator 'new' should instantiate a customized built-in element
+Pass	details: document.createElement() should instantiate a customized built-in element
+Pass	details: innerHTML should instantiate a customized built-in element
+Pass	dfn: Define a customized built-in element
+Pass	dfn: Operator 'new' should instantiate a customized built-in element
+Pass	dfn: document.createElement() should instantiate a customized built-in element
+Pass	dfn: innerHTML should instantiate a customized built-in element
+Pass	div: Define a customized built-in element
+Pass	div: Operator 'new' should instantiate a customized built-in element
+Pass	div: document.createElement() should instantiate a customized built-in element
+Pass	div: innerHTML should instantiate a customized built-in element
+Pass	dl: Define a customized built-in element
+Pass	dl: Operator 'new' should instantiate a customized built-in element
+Pass	dl: document.createElement() should instantiate a customized built-in element
+Pass	dl: innerHTML should instantiate a customized built-in element
+Pass	dt: Define a customized built-in element
+Pass	dt: Operator 'new' should instantiate a customized built-in element
+Pass	dt: document.createElement() should instantiate a customized built-in element
+Pass	dt: innerHTML should instantiate a customized built-in element
+Pass	em: Define a customized built-in element
+Pass	em: Operator 'new' should instantiate a customized built-in element
+Pass	em: document.createElement() should instantiate a customized built-in element
+Pass	em: innerHTML should instantiate a customized built-in element
+Pass	embed: Define a customized built-in element
+Pass	embed: Operator 'new' should instantiate a customized built-in element
+Pass	embed: document.createElement() should instantiate a customized built-in element
+Pass	embed: innerHTML should instantiate a customized built-in element
+Pass	fieldset: Define a customized built-in element
+Pass	fieldset: Operator 'new' should instantiate a customized built-in element
+Pass	fieldset: document.createElement() should instantiate a customized built-in element
+Pass	fieldset: innerHTML should instantiate a customized built-in element
+Pass	figcaption: Define a customized built-in element
+Pass	figcaption: Operator 'new' should instantiate a customized built-in element
+Pass	figcaption: document.createElement() should instantiate a customized built-in element
+Pass	figcaption: innerHTML should instantiate a customized built-in element
+Pass	figure: Define a customized built-in element
+Pass	figure: Operator 'new' should instantiate a customized built-in element
+Pass	figure: document.createElement() should instantiate a customized built-in element
+Pass	figure: innerHTML should instantiate a customized built-in element
+Pass	footer: Define a customized built-in element
+Pass	footer: Operator 'new' should instantiate a customized built-in element
+Pass	footer: document.createElement() should instantiate a customized built-in element
+Pass	footer: innerHTML should instantiate a customized built-in element
+Pass	form: Define a customized built-in element
+Pass	form: Operator 'new' should instantiate a customized built-in element
+Pass	form: document.createElement() should instantiate a customized built-in element
+Pass	form: innerHTML should instantiate a customized built-in element
+Pass	h1: Define a customized built-in element
+Pass	h1: Operator 'new' should instantiate a customized built-in element
+Pass	h1: document.createElement() should instantiate a customized built-in element
+Pass	h1: innerHTML should instantiate a customized built-in element
+Pass	h2: Define a customized built-in element
+Pass	h2: Operator 'new' should instantiate a customized built-in element
+Pass	h2: document.createElement() should instantiate a customized built-in element
+Pass	h2: innerHTML should instantiate a customized built-in element
+Pass	h3: Define a customized built-in element
+Pass	h3: Operator 'new' should instantiate a customized built-in element
+Pass	h3: document.createElement() should instantiate a customized built-in element
+Pass	h3: innerHTML should instantiate a customized built-in element
+Pass	h4: Define a customized built-in element
+Pass	h4: Operator 'new' should instantiate a customized built-in element
+Pass	h4: document.createElement() should instantiate a customized built-in element
+Pass	h4: innerHTML should instantiate a customized built-in element
+Pass	h5: Define a customized built-in element
+Pass	h5: Operator 'new' should instantiate a customized built-in element
+Pass	h5: document.createElement() should instantiate a customized built-in element
+Pass	h5: innerHTML should instantiate a customized built-in element
+Pass	h6: Define a customized built-in element
+Pass	h6: Operator 'new' should instantiate a customized built-in element
+Pass	h6: document.createElement() should instantiate a customized built-in element
+Pass	h6: innerHTML should instantiate a customized built-in element
+Pass	header: Define a customized built-in element
+Pass	header: Operator 'new' should instantiate a customized built-in element
+Pass	header: document.createElement() should instantiate a customized built-in element
+Pass	header: innerHTML should instantiate a customized built-in element
+Pass	hgroup: Define a customized built-in element
+Pass	hgroup: Operator 'new' should instantiate a customized built-in element
+Pass	hgroup: document.createElement() should instantiate a customized built-in element
+Pass	hgroup: innerHTML should instantiate a customized built-in element
+Pass	hr: Define a customized built-in element
+Pass	hr: Operator 'new' should instantiate a customized built-in element
+Pass	hr: document.createElement() should instantiate a customized built-in element
+Pass	hr: innerHTML should instantiate a customized built-in element
+Pass	html: Define a customized built-in element
+Pass	html: Operator 'new' should instantiate a customized built-in element
+Pass	html: document.createElement() should instantiate a customized built-in element
+Pass	html: document parser should instantiate a customized built-in element
+Pass	i: Define a customized built-in element
+Pass	i: Operator 'new' should instantiate a customized built-in element
+Pass	i: document.createElement() should instantiate a customized built-in element
+Pass	i: innerHTML should instantiate a customized built-in element
+Pass	iframe: Define a customized built-in element
+Pass	iframe: Operator 'new' should instantiate a customized built-in element
+Pass	iframe: document.createElement() should instantiate a customized built-in element
+Pass	iframe: innerHTML should instantiate a customized built-in element
+Pass	img: Define a customized built-in element
+Pass	img: Operator 'new' should instantiate a customized built-in element
+Pass	img: document.createElement() should instantiate a customized built-in element
+Pass	img: innerHTML should instantiate a customized built-in element
+Pass	input: Define a customized built-in element
+Pass	input: Operator 'new' should instantiate a customized built-in element
+Pass	input: document.createElement() should instantiate a customized built-in element
+Pass	input: innerHTML should instantiate a customized built-in element
+Pass	ins: Define a customized built-in element
+Pass	ins: Operator 'new' should instantiate a customized built-in element
+Pass	ins: document.createElement() should instantiate a customized built-in element
+Pass	ins: innerHTML should instantiate a customized built-in element
+Pass	kbd: Define a customized built-in element
+Pass	kbd: Operator 'new' should instantiate a customized built-in element
+Pass	kbd: document.createElement() should instantiate a customized built-in element
+Pass	kbd: innerHTML should instantiate a customized built-in element
+Pass	label: Define a customized built-in element
+Pass	label: Operator 'new' should instantiate a customized built-in element
+Pass	label: document.createElement() should instantiate a customized built-in element
+Pass	label: innerHTML should instantiate a customized built-in element
+Pass	legend: Define a customized built-in element
+Pass	legend: Operator 'new' should instantiate a customized built-in element
+Pass	legend: document.createElement() should instantiate a customized built-in element
+Pass	legend: innerHTML should instantiate a customized built-in element
+Pass	li: Define a customized built-in element
+Pass	li: Operator 'new' should instantiate a customized built-in element
+Pass	li: document.createElement() should instantiate a customized built-in element
+Pass	li: innerHTML should instantiate a customized built-in element
+Pass	link: Define a customized built-in element
+Pass	link: Operator 'new' should instantiate a customized built-in element
+Pass	link: document.createElement() should instantiate a customized built-in element
+Pass	link: innerHTML should instantiate a customized built-in element
+Pass	main: Define a customized built-in element
+Pass	main: Operator 'new' should instantiate a customized built-in element
+Pass	main: document.createElement() should instantiate a customized built-in element
+Pass	main: innerHTML should instantiate a customized built-in element
+Pass	map: Define a customized built-in element
+Pass	map: Operator 'new' should instantiate a customized built-in element
+Pass	map: document.createElement() should instantiate a customized built-in element
+Pass	map: innerHTML should instantiate a customized built-in element
+Pass	mark: Define a customized built-in element
+Pass	mark: Operator 'new' should instantiate a customized built-in element
+Pass	mark: document.createElement() should instantiate a customized built-in element
+Pass	mark: innerHTML should instantiate a customized built-in element
+Pass	menu: Define a customized built-in element
+Pass	menu: Operator 'new' should instantiate a customized built-in element
+Pass	menu: document.createElement() should instantiate a customized built-in element
+Pass	menu: innerHTML should instantiate a customized built-in element
+Pass	meta: Define a customized built-in element
+Pass	meta: Operator 'new' should instantiate a customized built-in element
+Pass	meta: document.createElement() should instantiate a customized built-in element
+Pass	meta: innerHTML should instantiate a customized built-in element
+Pass	meter: Define a customized built-in element
+Pass	meter: Operator 'new' should instantiate a customized built-in element
+Pass	meter: document.createElement() should instantiate a customized built-in element
+Pass	meter: innerHTML should instantiate a customized built-in element
+Pass	nav: Define a customized built-in element
+Pass	nav: Operator 'new' should instantiate a customized built-in element
+Pass	nav: document.createElement() should instantiate a customized built-in element
+Pass	nav: innerHTML should instantiate a customized built-in element
+Pass	noscript: Define a customized built-in element
+Pass	noscript: Operator 'new' should instantiate a customized built-in element
+Pass	noscript: document.createElement() should instantiate a customized built-in element
+Pass	noscript: innerHTML should instantiate a customized built-in element
+Pass	object: Define a customized built-in element
+Pass	object: Operator 'new' should instantiate a customized built-in element
+Pass	object: document.createElement() should instantiate a customized built-in element
+Pass	object: innerHTML should instantiate a customized built-in element
+Pass	ol: Define a customized built-in element
+Pass	ol: Operator 'new' should instantiate a customized built-in element
+Pass	ol: document.createElement() should instantiate a customized built-in element
+Pass	ol: innerHTML should instantiate a customized built-in element
+Pass	optgroup: Define a customized built-in element
+Pass	optgroup: Operator 'new' should instantiate a customized built-in element
+Pass	optgroup: document.createElement() should instantiate a customized built-in element
+Pass	optgroup: innerHTML should instantiate a customized built-in element
+Pass	option: Define a customized built-in element
+Pass	option: Operator 'new' should instantiate a customized built-in element
+Pass	option: document.createElement() should instantiate a customized built-in element
+Pass	option: innerHTML should instantiate a customized built-in element
+Pass	output: Define a customized built-in element
+Pass	output: Operator 'new' should instantiate a customized built-in element
+Pass	output: document.createElement() should instantiate a customized built-in element
+Pass	output: innerHTML should instantiate a customized built-in element
+Pass	p: Define a customized built-in element
+Pass	p: Operator 'new' should instantiate a customized built-in element
+Pass	p: document.createElement() should instantiate a customized built-in element
+Pass	p: innerHTML should instantiate a customized built-in element
+Pass	param: Define a customized built-in element
+Pass	param: Operator 'new' should instantiate a customized built-in element
+Pass	param: document.createElement() should instantiate a customized built-in element
+Pass	param: innerHTML should instantiate a customized built-in element
+Pass	picture: Define a customized built-in element
+Pass	picture: Operator 'new' should instantiate a customized built-in element
+Pass	picture: document.createElement() should instantiate a customized built-in element
+Pass	picture: innerHTML should instantiate a customized built-in element
+Pass	pre: Define a customized built-in element
+Pass	pre: Operator 'new' should instantiate a customized built-in element
+Pass	pre: document.createElement() should instantiate a customized built-in element
+Pass	pre: innerHTML should instantiate a customized built-in element
+Pass	progress: Define a customized built-in element
+Pass	progress: Operator 'new' should instantiate a customized built-in element
+Pass	progress: document.createElement() should instantiate a customized built-in element
+Pass	progress: innerHTML should instantiate a customized built-in element
+Pass	q: Define a customized built-in element
+Pass	q: Operator 'new' should instantiate a customized built-in element
+Pass	q: document.createElement() should instantiate a customized built-in element
+Pass	q: innerHTML should instantiate a customized built-in element
+Pass	rp: Define a customized built-in element
+Pass	rp: Operator 'new' should instantiate a customized built-in element
+Pass	rp: document.createElement() should instantiate a customized built-in element
+Pass	rp: innerHTML should instantiate a customized built-in element
+Pass	rt: Define a customized built-in element
+Pass	rt: Operator 'new' should instantiate a customized built-in element
+Pass	rt: document.createElement() should instantiate a customized built-in element
+Pass	rt: innerHTML should instantiate a customized built-in element
+Pass	ruby: Define a customized built-in element
+Pass	ruby: Operator 'new' should instantiate a customized built-in element
+Pass	ruby: document.createElement() should instantiate a customized built-in element
+Pass	ruby: innerHTML should instantiate a customized built-in element
+Pass	s: Define a customized built-in element
+Pass	s: Operator 'new' should instantiate a customized built-in element
+Pass	s: document.createElement() should instantiate a customized built-in element
+Pass	s: innerHTML should instantiate a customized built-in element
+Pass	samp: Define a customized built-in element
+Pass	samp: Operator 'new' should instantiate a customized built-in element
+Pass	samp: document.createElement() should instantiate a customized built-in element
+Pass	samp: innerHTML should instantiate a customized built-in element
+Pass	script: Define a customized built-in element
+Pass	script: Operator 'new' should instantiate a customized built-in element
+Pass	script: document.createElement() should instantiate a customized built-in element
+Pass	script: innerHTML should instantiate a customized built-in element
+Pass	section: Define a customized built-in element
+Pass	section: Operator 'new' should instantiate a customized built-in element
+Pass	section: document.createElement() should instantiate a customized built-in element
+Pass	section: innerHTML should instantiate a customized built-in element
+Pass	select: Define a customized built-in element
+Pass	select: Operator 'new' should instantiate a customized built-in element
+Pass	select: document.createElement() should instantiate a customized built-in element
+Pass	select: innerHTML should instantiate a customized built-in element
+Pass	small: Define a customized built-in element
+Pass	small: Operator 'new' should instantiate a customized built-in element
+Pass	small: document.createElement() should instantiate a customized built-in element
+Pass	small: innerHTML should instantiate a customized built-in element
+Pass	source: Define a customized built-in element
+Pass	source: Operator 'new' should instantiate a customized built-in element
+Pass	source: document.createElement() should instantiate a customized built-in element
+Pass	source: innerHTML should instantiate a customized built-in element
+Pass	span: Define a customized built-in element
+Pass	span: Operator 'new' should instantiate a customized built-in element
+Pass	span: document.createElement() should instantiate a customized built-in element
+Pass	span: innerHTML should instantiate a customized built-in element
+Pass	strong: Define a customized built-in element
+Pass	strong: Operator 'new' should instantiate a customized built-in element
+Pass	strong: document.createElement() should instantiate a customized built-in element
+Pass	strong: innerHTML should instantiate a customized built-in element
+Pass	style: Define a customized built-in element
+Pass	style: Operator 'new' should instantiate a customized built-in element
+Pass	style: document.createElement() should instantiate a customized built-in element
+Pass	style: innerHTML should instantiate a customized built-in element
+Pass	sub: Define a customized built-in element
+Pass	sub: Operator 'new' should instantiate a customized built-in element
+Pass	sub: document.createElement() should instantiate a customized built-in element
+Pass	sub: innerHTML should instantiate a customized built-in element
+Pass	summary: Define a customized built-in element
+Pass	summary: Operator 'new' should instantiate a customized built-in element
+Pass	summary: document.createElement() should instantiate a customized built-in element
+Pass	summary: innerHTML should instantiate a customized built-in element
+Pass	sup: Define a customized built-in element
+Pass	sup: Operator 'new' should instantiate a customized built-in element
+Pass	sup: document.createElement() should instantiate a customized built-in element
+Pass	sup: innerHTML should instantiate a customized built-in element
+Pass	table: Define a customized built-in element
+Pass	table: Operator 'new' should instantiate a customized built-in element
+Pass	table: document.createElement() should instantiate a customized built-in element
+Pass	table: innerHTML should instantiate a customized built-in element
+Pass	tbody: Define a customized built-in element
+Pass	tbody: Operator 'new' should instantiate a customized built-in element
+Pass	tbody: document.createElement() should instantiate a customized built-in element
+Pass	tbody: innerHTML should instantiate a customized built-in element
+Pass	td: Define a customized built-in element
+Pass	td: Operator 'new' should instantiate a customized built-in element
+Pass	td: document.createElement() should instantiate a customized built-in element
+Pass	td: innerHTML should instantiate a customized built-in element
+Pass	template: Define a customized built-in element
+Pass	template: Operator 'new' should instantiate a customized built-in element
+Pass	template: document.createElement() should instantiate a customized built-in element
+Pass	template: innerHTML should instantiate a customized built-in element
+Pass	textarea: Define a customized built-in element
+Pass	textarea: Operator 'new' should instantiate a customized built-in element
+Pass	textarea: document.createElement() should instantiate a customized built-in element
+Pass	textarea: innerHTML should instantiate a customized built-in element
+Pass	tfoot: Define a customized built-in element
+Pass	tfoot: Operator 'new' should instantiate a customized built-in element
+Pass	tfoot: document.createElement() should instantiate a customized built-in element
+Pass	tfoot: innerHTML should instantiate a customized built-in element
+Pass	th: Define a customized built-in element
+Pass	th: Operator 'new' should instantiate a customized built-in element
+Pass	th: document.createElement() should instantiate a customized built-in element
+Pass	th: innerHTML should instantiate a customized built-in element
+Pass	thead: Define a customized built-in element
+Pass	thead: Operator 'new' should instantiate a customized built-in element
+Pass	thead: document.createElement() should instantiate a customized built-in element
+Pass	thead: innerHTML should instantiate a customized built-in element
+Pass	time: Define a customized built-in element
+Pass	time: Operator 'new' should instantiate a customized built-in element
+Pass	time: document.createElement() should instantiate a customized built-in element
+Pass	time: innerHTML should instantiate a customized built-in element
+Pass	title: Define a customized built-in element
+Pass	title: Operator 'new' should instantiate a customized built-in element
+Pass	title: document.createElement() should instantiate a customized built-in element
+Pass	title: innerHTML should instantiate a customized built-in element
+Pass	tr: Define a customized built-in element
+Pass	tr: Operator 'new' should instantiate a customized built-in element
+Pass	tr: document.createElement() should instantiate a customized built-in element
+Pass	tr: innerHTML should instantiate a customized built-in element
+Pass	track: Define a customized built-in element
+Pass	track: Operator 'new' should instantiate a customized built-in element
+Pass	track: document.createElement() should instantiate a customized built-in element
+Pass	track: innerHTML should instantiate a customized built-in element
+Pass	u: Define a customized built-in element
+Pass	u: Operator 'new' should instantiate a customized built-in element
+Pass	u: document.createElement() should instantiate a customized built-in element
+Pass	u: innerHTML should instantiate a customized built-in element
+Pass	ul: Define a customized built-in element
+Pass	ul: Operator 'new' should instantiate a customized built-in element
+Pass	ul: document.createElement() should instantiate a customized built-in element
+Pass	ul: innerHTML should instantiate a customized built-in element
+Pass	var: Define a customized built-in element
+Pass	var: Operator 'new' should instantiate a customized built-in element
+Pass	var: document.createElement() should instantiate a customized built-in element
+Pass	var: innerHTML should instantiate a customized built-in element
+Pass	video: Define a customized built-in element
+Pass	video: Operator 'new' should instantiate a customized built-in element
+Pass	video: document.createElement() should instantiate a customized built-in element
+Pass	video: innerHTML should instantiate a customized built-in element
+Pass	wbr: Define a customized built-in element
+Pass	wbr: Operator 'new' should instantiate a customized built-in element
+Pass	wbr: document.createElement() should instantiate a customized built-in element
+Pass	wbr: innerHTML should instantiate a customized built-in element
+Pass	datalist: Define a customized built-in element
+Pass	datalist: Operator 'new' should instantiate a customized built-in element
+Pass	datalist: document.createElement() should instantiate a customized built-in element
+Pass	datalist: innerHTML should instantiate a customized built-in element
+Pass	dialog: Define a customized built-in element
+Pass	dialog: Operator 'new' should instantiate a customized built-in element
+Pass	dialog: document.createElement() should instantiate a customized built-in element
+Pass	dialog: innerHTML should instantiate a customized built-in element
+Pass	slot: Define a customized built-in element
+Pass	slot: Operator 'new' should instantiate a customized built-in element
+Pass	slot: document.createElement() should instantiate a customized built-in element
+Pass	slot: innerHTML should instantiate a customized built-in element
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/input/wpt-import/custom-elements/builtin-coverage.html b/Tests/LibWeb/Text/input/wpt-import/custom-elements/builtin-coverage.html
new file mode 100644
index 00000000000..bebffbc8aa1
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/custom-elements/builtin-coverage.html
@@ -0,0 +1,182 @@
+<!DOCTYPE html>
+<html is="my-html">
+<head>
+<meta charset="utf-8">
+<meta name="help" content="https://html.spec.whatwg.org/multipage/custom-elements.html#element-definition">
+<script src="../resources/testharness.js"></script>
+<script src="../resources/testharnessreport.js"></script>
+</head>
+<body is="my-body">
+<div id="container"></div>
+<script>
+let testData = [
+  {tag: 'a', interface: 'HTMLAnchorElement'},
+  {tag: 'abbr', interface: 'HTMLElement'},
+  {tag: 'address', interface: 'HTMLElement'},
+  {tag: 'area', interface: 'HTMLAreaElement'},
+  {tag: 'article', interface: 'HTMLElement'},
+  {tag: 'aside', interface: 'HTMLElement'},
+  {tag: 'audio', interface: 'HTMLAudioElement'},
+  {tag: 'b', interface: 'HTMLElement'},
+  {tag: 'base', interface: 'HTMLBaseElement'},
+  {tag: 'bdi', interface: 'HTMLElement'},
+  {tag: 'bdo', interface: 'HTMLElement'},
+  {tag: 'blockquote', interface: 'HTMLQuoteElement'},
+  {tag: 'body', interface: 'HTMLBodyElement', parsing: 'document'},
+  {tag: 'br', interface: 'HTMLBRElement'},
+  {tag: 'button', interface: 'HTMLButtonElement'},
+  {tag: 'canvas', interface: 'HTMLCanvasElement'},
+  {tag: 'caption', interface: 'HTMLTableCaptionElement', parsing: 'table'},
+  {tag: 'cite', interface: 'HTMLElement'},
+  {tag: 'code', interface: 'HTMLElement'},
+  {tag: 'col', interface: 'HTMLTableColElement', parsing: 'table'},
+  {tag: 'colgroup', interface: 'HTMLTableColElement', parsing: 'table'},
+  {tag: 'data', interface: 'HTMLDataElement'},
+  {tag: 'dd', interface: 'HTMLElement'},
+  {tag: 'del', interface: 'HTMLModElement'},
+  {tag: 'details', interface: 'HTMLDetailsElement'},
+  {tag: 'dfn', interface: 'HTMLElement'},
+  {tag: 'div', interface: 'HTMLDivElement'},
+  {tag: 'dl', interface: 'HTMLDListElement'},
+  {tag: 'dt', interface: 'HTMLElement'},
+  {tag: 'em', interface: 'HTMLElement'},
+  {tag: 'embed', interface: 'HTMLEmbedElement'},
+  {tag: 'fieldset', interface: 'HTMLFieldSetElement'},
+  {tag: 'figcaption', interface: 'HTMLElement'},
+  {tag: 'figure', interface: 'HTMLElement'},
+  {tag: 'footer', interface: 'HTMLElement'},
+  {tag: 'form', interface: 'HTMLFormElement'},
+  {tag: 'h1', interface: 'HTMLHeadingElement'},
+  {tag: 'h2', interface: 'HTMLHeadingElement'},
+  {tag: 'h3', interface: 'HTMLHeadingElement'},
+  {tag: 'h4', interface: 'HTMLHeadingElement'},
+  {tag: 'h5', interface: 'HTMLHeadingElement'},
+  {tag: 'h6', interface: 'HTMLHeadingElement'},
+  {tag: 'header', interface: 'HTMLElement'},
+  {tag: 'hgroup', interface: 'HTMLElement'},
+  {tag: 'hr', interface: 'HTMLHRElement'},
+  {tag: 'html', interface: 'HTMLHtmlElement', parsing: 'document'},
+  {tag: 'i', interface: 'HTMLElement'},
+  {tag: 'iframe', interface: 'HTMLIFrameElement'},
+  {tag: 'img', interface: 'HTMLImageElement'},
+  {tag: 'input', interface: 'HTMLInputElement'},
+  {tag: 'ins', interface: 'HTMLModElement'},
+  {tag: 'kbd', interface: 'HTMLElement'},
+  {tag: 'label', interface: 'HTMLLabelElement'},
+  {tag: 'legend', interface: 'HTMLLegendElement'},
+  {tag: 'li', interface: 'HTMLLIElement'},
+  {tag: 'link', interface: 'HTMLLinkElement'},
+  {tag: 'main', interface: 'HTMLElement'},
+  {tag: 'map', interface: 'HTMLMapElement'},
+  {tag: 'mark', interface: 'HTMLElement'},
+  {tag: 'menu', interface: 'HTMLMenuElement'},
+  {tag: 'meta', interface: 'HTMLMetaElement'},
+  {tag: 'meter', interface: 'HTMLMeterElement'},
+  {tag: 'nav', interface: 'HTMLElement'},
+  {tag: 'noscript', interface: 'HTMLElement'},
+  {tag: 'object', interface: 'HTMLObjectElement'},
+  {tag: 'ol', interface: 'HTMLOListElement'},
+  {tag: 'optgroup', interface: 'HTMLOptGroupElement'},
+  {tag: 'option', interface: 'HTMLOptionElement'},
+  {tag: 'output', interface: 'HTMLOutputElement'},
+  {tag: 'p', interface: 'HTMLParagraphElement'},
+  {tag: 'param', interface: 'HTMLParamElement'},
+  {tag: 'picture', interface: 'HTMLPictureElement'},
+  {tag: 'pre', interface: 'HTMLPreElement'},
+  {tag: 'progress', interface: 'HTMLProgressElement'},
+  {tag: 'q', interface: 'HTMLQuoteElement'},
+  {tag: 'rp', interface: 'HTMLElement'},
+  {tag: 'rt', interface: 'HTMLElement'},
+  {tag: 'ruby', interface: 'HTMLElement'},
+  {tag: 's', interface: 'HTMLElement'},
+  {tag: 'samp', interface: 'HTMLElement'},
+  {tag: 'script', interface: 'HTMLScriptElement'},
+  {tag: 'section', interface: 'HTMLElement'},
+  {tag: 'select', interface: 'HTMLSelectElement'},
+  {tag: 'small', interface: 'HTMLElement'},
+  {tag: 'source', interface: 'HTMLSourceElement'},
+  {tag: 'span', interface: 'HTMLSpanElement'},
+  {tag: 'strong', interface: 'HTMLElement'},
+  {tag: 'style', interface: 'HTMLStyleElement'},
+  {tag: 'sub', interface: 'HTMLElement'},
+  {tag: 'summary', interface: 'HTMLElement'},
+  {tag: 'sup', interface: 'HTMLElement'},
+  {tag: 'table', interface: 'HTMLTableElement'},
+  {tag: 'tbody', interface: 'HTMLTableSectionElement', parsing: 'table'},
+  {tag: 'td', interface: 'HTMLTableCellElement', parsing: 'table'},
+  {tag: 'template', interface: 'HTMLTemplateElement'},
+  {tag: 'textarea', interface: 'HTMLTextAreaElement'},
+  {tag: 'tfoot', interface: 'HTMLTableSectionElement', parsing: 'table'},
+  {tag: 'th', interface: 'HTMLTableCellElement', parsing: 'table'},
+  {tag: 'thead', interface: 'HTMLTableSectionElement', parsing: 'table'},
+  {tag: 'time', interface: 'HTMLTimeElement'},
+  {tag: 'title', interface: 'HTMLTitleElement'},
+  {tag: 'tr', interface: 'HTMLTableRowElement', parsing: 'table'},
+  {tag: 'track', interface: 'HTMLTrackElement'},
+  {tag: 'u', interface: 'HTMLElement'},
+  {tag: 'ul', interface: 'HTMLUListElement'},
+  {tag: 'var', interface: 'HTMLElement'},
+  {tag: 'video', interface: 'HTMLVideoElement'},
+  {tag: 'wbr', interface: 'HTMLElement'},
+];
+// HTMLDataListElement isn't implemented by all major browsers yet.
+if (window.HTMLDataListElement) {
+  testData.push({tag: 'datalist', interface: 'HTMLDataListElement'});
+}
+// HTMLDialogElement isn't implemented by all major browsers yet.
+if (window.HTMLDialogElement) {
+  testData.push({tag: 'dialog', interface: 'HTMLDialogElement'});
+}
+// HTMLSlotElement isn't implemented by all major browsers yet.
+if (window.HTMLSlotElement) {
+  testData.push({tag: 'slot', interface: 'HTMLSlotElement'});
+}
+
+for (const t of testData) {
+  test(() => {
+    let name = 'my-' + t.tag;
+    let klass = eval(`(class extends ${t.interface} {})`);
+    customElements.define(name, klass, { extends: t.tag });
+
+    test(() => {
+      let customized = new klass();
+      assert_equals(customized.constructor, klass);
+      assert_equals(customized.cloneNode().constructor, klass,
+                    'Cloning a customized built-in element should succeed.');
+    }, `${t.tag}: Operator 'new' should instantiate a customized built-in element`);
+
+    test(() => {
+      let customized = document.createElement(t.tag, { is: name });
+      assert_equals(customized.constructor, klass);
+      assert_equals(customized.cloneNode().constructor, klass,
+                    'Cloning a customized built-in element should succeed.');
+    }, `${t.tag}: document.createElement() should instantiate a customized built-in element`);
+
+    if (t.parsing == 'document') {
+      let test = async_test(`${t.tag}: document parser should instantiate a customized built-in element`);
+      window.addEventListener('load', test.step_func_done(() => {
+        let customized = document.querySelector(t.tag);
+        assert_equals(customized.constructor, klass);
+        assert_equals(customized.cloneNode().constructor, klass,
+                      'Cloning a customized built-in element should succeed.');
+      }));
+      return;
+    }
+    test(() => {
+      let container = document.getElementById('container');
+      if (t.parsing == 'table') {
+        container.innerHTML = `<table><${t.tag} is="${name}" id="${name}">`;
+      } else {
+        container.innerHTML = `<${t.tag} is="${name}" id="${name}">`;
+      }
+      let customized = document.getElementById(name);
+      assert_equals(customized.constructor, klass);
+      assert_equals(customized.cloneNode().constructor, klass,
+                    'Cloning a customized built-in element should succeed.');
+    }, `${t.tag}: innerHTML should instantiate a customized built-in element`);
+
+  }, `${t.tag}: Define a customized built-in element`);
+}
+</script>
+</body>
+</html>