diff --git a/Userland/Libraries/LibWeb/HTML/DOMStringMap.cpp b/Userland/Libraries/LibWeb/HTML/DOMStringMap.cpp
index 900538a466..c3121c7ee2 100644
--- a/Userland/Libraries/LibWeb/HTML/DOMStringMap.cpp
+++ b/Userland/Libraries/LibWeb/HTML/DOMStringMap.cpp
@@ -19,7 +19,7 @@ JS::NonnullGCPtr<DOMStringMap> DOMStringMap::create(DOM::Element& element)
 }
 
 DOMStringMap::DOMStringMap(DOM::Element& element)
-    : PlatformObject(Bindings::cached_web_prototype(element.realm(), "DOMStringMap"))
+    : LegacyPlatformObject(Bindings::cached_web_prototype(element.realm(), "DOMStringMap"))
     , m_associated_element(element)
 {
 }
@@ -183,4 +183,9 @@ bool DOMStringMap::delete_existing_named_property(String const& name)
     return true;
 }
 
+JS::Value DOMStringMap::named_item_value(FlyString const& name) const
+{
+    return js_string(vm(), determine_value_of_named_property(name));
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/HTML/DOMStringMap.h b/Userland/Libraries/LibWeb/HTML/DOMStringMap.h
index 2b98b53f23..617505657e 100644
--- a/Userland/Libraries/LibWeb/HTML/DOMStringMap.h
+++ b/Userland/Libraries/LibWeb/HTML/DOMStringMap.h
@@ -7,22 +7,20 @@
 
 #pragma once
 
-#include <LibWeb/Bindings/PlatformObject.h>
+#include <LibWeb/Bindings/LegacyPlatformObject.h>
 #include <LibWeb/Forward.h>
 
 namespace Web::HTML {
 
 // https://html.spec.whatwg.org/multipage/dom.html#domstringmap
-class DOMStringMap final : public Bindings::PlatformObject {
-    WEB_PLATFORM_OBJECT(DOMStringMap, Bindings::PlatformObject);
+class DOMStringMap final : public Bindings::LegacyPlatformObject {
+    WEB_PLATFORM_OBJECT(DOMStringMap, Bindings::LegacyPlatformObject);
 
 public:
     static JS::NonnullGCPtr<DOMStringMap> create(DOM::Element&);
 
     virtual ~DOMStringMap() override;
 
-    Vector<String> supported_property_names() const;
-
     String determine_value_of_named_property(String const&) const;
 
     WebIDL::ExceptionOr<void> set_value_of_new_named_property(String const&, String const&);
@@ -35,6 +33,10 @@ private:
 
     virtual void visit_edges(Cell::Visitor&) override;
 
+    // ^LegacyPlatformObject
+    virtual JS::Value named_item_value(FlyString const&) const override;
+    virtual Vector<String> supported_property_names() const override;
+
     struct NameValuePair {
         String name;
         String value;