diff --git a/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.h b/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.h
index 0edc146398..9039205418 100644
--- a/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.h
+++ b/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.h
@@ -13,9 +13,9 @@
 namespace Web::IntersectionObserver {
 
 struct IntersectionObserverInit {
-    DOM::Node* root { nullptr };
+    Optional<Variant<NonnullRefPtr<DOM::Element>, NonnullRefPtr<DOM::Document>>> root;
     String root_margin { "0px"sv };
-    JS::Value threshold { 0 };
+    Variant<double, Vector<double>> threshold { 0 };
 };
 
 // https://w3c.github.io/IntersectionObserver/#intersection-observer-interface
diff --git a/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.idl b/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.idl
index 1cc24b6a93..122859d825 100644
--- a/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.idl
+++ b/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.idl
@@ -1,3 +1,4 @@
+#import <DOM/Document.idl>
 #import <DOM/Element.idl>
 #import <DOM/Node.idl>
 
@@ -16,11 +17,7 @@ interface IntersectionObserver {
 };
 
 dictionary IntersectionObserverInit {
-    // FIXME: Should be: (Element or Document)?
-    Node? root = null;
-
+    (Element or Document)? root = null;
     DOMString rootMargin = "0px";
-
-    // FIXME: Should be: (double or sequence<double>)
-    any threshold = 0;
+    (double or sequence<double>) threshold = 0;
 };