diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index dda2344b544..2e5e03d84a1 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -5131,7 +5131,7 @@ size_t Document::broadcast_active_resize_observations()
         }
 
         // 2. Let entries be an empty list of ResizeObserverEntryies.
-        Vector<JS::NonnullGCPtr<ResizeObserver::ResizeObserverEntry>> entries;
+        JS::MarkedVector<JS::NonnullGCPtr<ResizeObserver::ResizeObserverEntry>> entries(heap());
 
         // 3. For each observation in [[activeTargets]] perform these steps:
         for (auto const& observation : observer->active_targets()) {
diff --git a/Userland/Libraries/LibWeb/ResizeObserver/ResizeObserver.cpp b/Userland/Libraries/LibWeb/ResizeObserver/ResizeObserver.cpp
index 995ca7f7766..8111ef3cb57 100644
--- a/Userland/Libraries/LibWeb/ResizeObserver/ResizeObserver.cpp
+++ b/Userland/Libraries/LibWeb/ResizeObserver/ResizeObserver.cpp
@@ -97,7 +97,7 @@ void ResizeObserver::disconnect()
     m_active_targets.clear();
 }
 
-void ResizeObserver::invoke_callback(Vector<JS::NonnullGCPtr<ResizeObserverEntry>>& entries) const
+void ResizeObserver::invoke_callback(ReadonlySpan<JS::NonnullGCPtr<ResizeObserverEntry>> entries) const
 {
     auto& callback = *m_callback;
     auto& realm = callback.callback_context->realm();
diff --git a/Userland/Libraries/LibWeb/ResizeObserver/ResizeObserver.h b/Userland/Libraries/LibWeb/ResizeObserver/ResizeObserver.h
index 9e0a8886139..5eaa3132efb 100644
--- a/Userland/Libraries/LibWeb/ResizeObserver/ResizeObserver.h
+++ b/Userland/Libraries/LibWeb/ResizeObserver/ResizeObserver.h
@@ -31,7 +31,7 @@ public:
     void unobserve(DOM::Element& target);
     void disconnect();
 
-    void invoke_callback(Vector<JS::NonnullGCPtr<ResizeObserverEntry>>& entries) const;
+    void invoke_callback(ReadonlySpan<JS::NonnullGCPtr<ResizeObserverEntry>> entries) const;
 
     Vector<JS::NonnullGCPtr<ResizeObservation>>& observation_targets() { return m_observation_targets; }
     Vector<JS::NonnullGCPtr<ResizeObservation>>& active_targets() { return m_active_targets; }