diff --git a/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp b/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp
index b5bca1fe04..5caa2abdf9 100644
--- a/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp
+++ b/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp
@@ -46,7 +46,7 @@ void DOMImplementation::visit_edges(Cell::Visitor& visitor)
 }
 
 // https://dom.spec.whatwg.org/#dom-domimplementation-createdocument
-WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> DOMImplementation::create_document(Optional<String> const& namespace_, String const& qualified_name, JS::GCPtr<DocumentType> doctype) const
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> DOMImplementation::create_document(Optional<FlyString> const& namespace_, String const& qualified_name, JS::GCPtr<DocumentType> doctype) const
 {
     // 1. Let document be a new XMLDocument
     auto xml_document = XMLDocument::create(realm());
@@ -72,15 +72,10 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> DOMImplementation::create_docume
     xml_document->set_origin(document().origin());
 
     // 7. document’s content type is determined by namespace:
-    // FIXME: This conversion is ugly
-    Optional<FlyString> namespace_to_use;
-    if (namespace_.has_value())
-        namespace_to_use = namespace_.value();
-
-    if (namespace_to_use == Namespace::HTML) {
+    if (namespace_ == Namespace::HTML) {
         // -> HTML namespace
         xml_document->set_content_type("application/xhtml+xml"_string);
-    } else if (namespace_to_use == Namespace::SVG) {
+    } else if (namespace_ == Namespace::SVG) {
         // -> SVG namespace
         xml_document->set_content_type("image/svg+xml"_string);
     } else {
diff --git a/Userland/Libraries/LibWeb/DOM/DOMImplementation.h b/Userland/Libraries/LibWeb/DOM/DOMImplementation.h
index f9b777aa92..ab048a4daa 100644
--- a/Userland/Libraries/LibWeb/DOM/DOMImplementation.h
+++ b/Userland/Libraries/LibWeb/DOM/DOMImplementation.h
@@ -21,7 +21,7 @@ public:
     [[nodiscard]] static JS::NonnullGCPtr<DOMImplementation> create(Document&);
     virtual ~DOMImplementation();
 
-    WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> create_document(Optional<String> const&, String const&, JS::GCPtr<DocumentType>) const;
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> create_document(Optional<FlyString> const&, String const&, JS::GCPtr<DocumentType>) const;
     JS::NonnullGCPtr<Document> create_html_document(Optional<String> const& title) const;
     WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentType>> create_document_type(String const& qualified_name, String const& public_id, String const& system_id);
 
diff --git a/Userland/Libraries/LibWeb/DOM/DOMImplementation.idl b/Userland/Libraries/LibWeb/DOM/DOMImplementation.idl
index 14060e83ea..d30b107a72 100644
--- a/Userland/Libraries/LibWeb/DOM/DOMImplementation.idl
+++ b/Userland/Libraries/LibWeb/DOM/DOMImplementation.idl
@@ -5,7 +5,7 @@
 interface DOMImplementation {
 
     // FIXME: This should return XMLDocument instead of Document.
-    [NewObject] Document createDocument(DOMString? namespace, [LegacyNullToEmptyString] DOMString qualifiedName, optional DocumentType? doctype = null);
+    [NewObject] Document createDocument([FlyString] DOMString? namespace, [LegacyNullToEmptyString] DOMString qualifiedName, optional DocumentType? doctype = null);
     [NewObject] Document createHTMLDocument(optional DOMString title);
     [NewObject] DocumentType createDocumentType(DOMString qualifiedName, DOMString publicId, DOMString systemId);
 
diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index c8e8c72f3a..a2aab2061e 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -1426,15 +1426,10 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element(String c
 
 // https://dom.spec.whatwg.org/#dom-document-createelementns
 // https://dom.spec.whatwg.org/#internal-createelementns-steps
-WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element_ns(Optional<String> const& namespace_, String const& qualified_name, Variant<String, ElementCreationOptions> const& options)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element_ns(Optional<FlyString> const& namespace_, String const& qualified_name, Variant<String, ElementCreationOptions> const& options)
 {
-    // FIXME: This conversion is ugly
-    Optional<FlyString> namespace_to_use;
-    if (namespace_.has_value())
-        namespace_to_use = namespace_.value();
-
     // 1. Let namespace, prefix, and localName be the result of passing namespace and qualifiedName to validate and extract.
-    auto extracted_qualified_name = TRY(validate_and_extract(realm(), namespace_to_use, qualified_name));
+    auto extracted_qualified_name = TRY(validate_and_extract(realm(), namespace_, qualified_name));
 
     // 2. Let is be null.
     Optional<String> is_value;
@@ -3082,15 +3077,10 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> Document::create_attribute(String co
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createattributens
-WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> Document::create_attribute_ns(Optional<String> const& namespace_, String const& qualified_name)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> Document::create_attribute_ns(Optional<FlyString> const& namespace_, String const& qualified_name)
 {
-    // FIXME: This conversion is ugly
-    Optional<FlyString> namespace_to_use;
-    if (namespace_.has_value())
-        namespace_to_use = namespace_.value();
-
     // 1. Let namespace, prefix, and localName be the result of passing namespace and qualifiedName to validate and extract.
-    auto extracted_qualified_name = TRY(validate_and_extract(realm(), namespace_to_use, qualified_name));
+    auto extracted_qualified_name = TRY(validate_and_extract(realm(), namespace_, qualified_name));
 
     // 2. Return a new attribute whose namespace is namespace, namespace prefix is prefix, local name is localName, and node document is this.
 
diff --git a/Userland/Libraries/LibWeb/DOM/Document.h b/Userland/Libraries/LibWeb/DOM/Document.h
index d90d70cb71..4db04655e1 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.h
+++ b/Userland/Libraries/LibWeb/DOM/Document.h
@@ -238,14 +238,14 @@ public:
     HTML::EnvironmentSettingsObject& relevant_settings_object() const;
 
     WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> create_element(String const& local_name, Variant<String, ElementCreationOptions> const& options);
-    WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> create_element_ns(Optional<String> const& namespace_, String const& qualified_name, Variant<String, ElementCreationOptions> const& options);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> create_element_ns(Optional<FlyString> const& namespace_, String const& qualified_name, Variant<String, ElementCreationOptions> const& options);
     JS::NonnullGCPtr<DocumentFragment> create_document_fragment();
     JS::NonnullGCPtr<Text> create_text_node(String const& data);
     JS::NonnullGCPtr<Comment> create_comment(String const& data);
     WebIDL::ExceptionOr<JS::NonnullGCPtr<ProcessingInstruction>> create_processing_instruction(String const& target, String const& data);
 
     WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> create_attribute(String const& local_name);
-    WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> create_attribute_ns(Optional<String> const& namespace_, String const& qualified_name);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> create_attribute_ns(Optional<FlyString> const& namespace_, String const& qualified_name);
 
     WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> create_event(StringView interface);
     JS::NonnullGCPtr<Range> create_range();
diff --git a/Userland/Libraries/LibWeb/DOM/Document.idl b/Userland/Libraries/LibWeb/DOM/Document.idl
index c6dc9d4544..8640fec711 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.idl
+++ b/Userland/Libraries/LibWeb/DOM/Document.idl
@@ -76,14 +76,14 @@ interface Document : Node {
     readonly attribute HTMLCollection all;
 
     [CEReactions, NewObject] Element createElement(DOMString tagName, optional (DOMString or ElementCreationOptions) options = {});
-    [CEReactions, NewObject] Element createElementNS(DOMString? namespace, DOMString qualifiedName, optional (DOMString or ElementCreationOptions) options = {});
+    [CEReactions, NewObject] Element createElementNS([FlyString] DOMString? namespace, DOMString qualifiedName, optional (DOMString or ElementCreationOptions) options = {});
     DocumentFragment createDocumentFragment();
     Text createTextNode(DOMString data);
     Comment createComment(DOMString data);
     [NewObject] ProcessingInstruction createProcessingInstruction(DOMString target, DOMString data);
 
     [NewObject] Attr createAttribute(DOMString localName);
-    [NewObject] Attr createAttributeNS(DOMString? namespace, DOMString qualifiedName);
+    [NewObject] Attr createAttributeNS([FlyString] DOMString? namespace, DOMString qualifiedName);
 
     Range createRange();
     Event createEvent(DOMString interface);