diff --git a/Userland/Libraries/LibWeb/HTML/Window.cpp b/Userland/Libraries/LibWeb/HTML/Window.cpp
index b3285e3679..663f831be0 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Window.cpp
@@ -1506,7 +1506,7 @@ JS::NonnullGCPtr<CustomElementRegistry> Window::custom_elements()
 }
 
 // https://html.spec.whatwg.org/#document-tree-child-navigable-target-name-property-set
-OrderedHashMap<String, JS::NonnullGCPtr<Navigable>> Window::document_tree_child_navigable_target_name_property_set()
+OrderedHashMap<FlyString, JS::NonnullGCPtr<Navigable>> Window::document_tree_child_navigable_target_name_property_set()
 {
     // The document-tree child navigable target name property set of a Window object window is the return value of running these steps:
 
@@ -1514,7 +1514,7 @@ OrderedHashMap<String, JS::NonnullGCPtr<Navigable>> Window::document_tree_child_
     auto children = associated_document().document_tree_child_navigables();
 
     // 2. Let firstNamedChildren be an empty ordered set.
-    OrderedHashMap<String, JS::NonnullGCPtr<Navigable>> first_named_children;
+    OrderedHashMap<FlyString, JS::NonnullGCPtr<Navigable>> first_named_children;
 
     // 3. For each navigable of children:
     for (auto const& navigable : children) {
@@ -1534,7 +1534,7 @@ OrderedHashMap<String, JS::NonnullGCPtr<Navigable>> Window::document_tree_child_
     }
 
     // 4. Let names be an empty ordered set.
-    OrderedHashMap<String, JS::NonnullGCPtr<Navigable>> names;
+    OrderedHashMap<FlyString, JS::NonnullGCPtr<Navigable>> names;
 
     // 5. For each navigable of firstNamedChildren:
     for (auto const& [name, navigable] : first_named_children) {
diff --git a/Userland/Libraries/LibWeb/HTML/Window.h b/Userland/Libraries/LibWeb/HTML/Window.h
index 575e07ef26..a8c0768ab4 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.h
+++ b/Userland/Libraries/LibWeb/HTML/Window.h
@@ -201,7 +201,7 @@ public:
     static void set_inspector_object_exposed(bool);
     static void set_internals_object_exposed(bool);
 
-    [[nodiscard]] OrderedHashMap<String, JS::NonnullGCPtr<Navigable>> document_tree_child_navigable_target_name_property_set();
+    [[nodiscard]] OrderedHashMap<FlyString, JS::NonnullGCPtr<Navigable>> document_tree_child_navigable_target_name_property_set();
 
     [[nodiscard]] Vector<FlyString> supported_property_names();
     [[nodiscard]] WebIDL::ExceptionOr<JS::Value> named_item_value(FlyString const&);