diff --git a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp
index fb919fadf6..ecfa0cadf2 100644
--- a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp
+++ b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp
@@ -176,6 +176,23 @@ Attr const* NamedNodeMap::get_attribute(StringView qualified_name, size_t* item_
     return nullptr;
 }
 
+// https://dom.spec.whatwg.org/#concept-element-attributes-get-by-namespace
+Attr const* NamedNodeMap::get_attribute_ns(Optional<FlyString> const& namespace_, FlyString const& local_name, size_t* item_index) const
+{
+    // FIXME: We shouldn't need to do any conversion when looking up in the node map.
+    StringView namespace_view;
+    if (namespace_.has_value())
+        namespace_view = namespace_->bytes_as_string_view();
+
+    return get_attribute_ns(namespace_view, local_name, item_index);
+}
+
+// https://dom.spec.whatwg.org/#concept-element-attributes-get-by-namespace
+Attr* NamedNodeMap::get_attribute_ns(Optional<FlyString> const& namespace_, FlyString const& local_name, size_t* item_index)
+{
+    return const_cast<Attr*>(const_cast<NamedNodeMap const*>(this)->get_attribute_ns(namespace_, local_name, item_index));
+}
+
 // https://dom.spec.whatwg.org/#concept-element-attributes-get-by-namespace
 Attr* NamedNodeMap::get_attribute_ns(StringView namespace_, StringView local_name, size_t* item_index)
 {
diff --git a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h
index 82fd1d5af2..3c1591f97e 100644
--- a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h
+++ b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h
@@ -52,6 +52,9 @@ public:
     void replace_attribute(Attr& old_attribute, Attr& new_attribute, size_t old_attribute_index);
     void append_attribute(Attr& attribute);
 
+    Attr* get_attribute_ns(Optional<FlyString> const& namespace_, FlyString const& local_name, size_t* item_index = nullptr);
+    Attr const* get_attribute_ns(Optional<FlyString> const& namespace_, FlyString const& local_name, size_t* item_index = nullptr) const;
+
     // FIXME: This should take a 'FlyString cosnt&'
     Attr const* remove_attribute(StringView qualified_name);
     Attr const* remove_attribute_ns(StringView namespace_, StringView local_name);