diff --git a/Userland/Libraries/LibJS/Heap/Cell.h b/Userland/Libraries/LibJS/Heap/Cell.h
index c870a998ee..d3820616ac 100644
--- a/Userland/Libraries/LibJS/Heap/Cell.h
+++ b/Userland/Libraries/LibJS/Heap/Cell.h
@@ -77,6 +77,9 @@ public:
     virtual bool is_environment() const { return false; }
     virtual void visit_edges(Visitor&) { }
 
+    // This will be called on unmarked objects by the garbage collector in a separate pass before destruction.
+    virtual void finalize() { }
+
     Heap& heap() const;
     VM& vm() const;
 
diff --git a/Userland/Libraries/LibJS/Heap/Heap.cpp b/Userland/Libraries/LibJS/Heap/Heap.cpp
index a9860b9473..e7664761f6 100644
--- a/Userland/Libraries/LibJS/Heap/Heap.cpp
+++ b/Userland/Libraries/LibJS/Heap/Heap.cpp
@@ -106,6 +106,7 @@ void Heap::collect_garbage(CollectionType collection_type, bool print_report)
         gather_roots(roots);
         mark_live_cells(roots);
     }
+    finalize_unmarked_cells();
     sweep_dead_cells(print_report, collection_measurement_timer);
 }
 
@@ -231,6 +232,17 @@ void Heap::mark_live_cells(HashTable<Cell*> const& roots)
     m_uprooted_cells.clear();
 }
 
+void Heap::finalize_unmarked_cells()
+{
+    for_each_block([&](auto& block) {
+        block.template for_each_cell_in_state<Cell::State::Live>([](Cell* cell) {
+            if (!cell->is_marked())
+                cell->finalize();
+        });
+        return IterationDecision::Continue;
+    });
+}
+
 void Heap::sweep_dead_cells(bool print_report, Core::ElapsedTimer const& measurement_timer)
 {
     dbgln_if(HEAP_DEBUG, "sweep_dead_cells:");
diff --git a/Userland/Libraries/LibJS/Heap/Heap.h b/Userland/Libraries/LibJS/Heap/Heap.h
index 435d7c6364..f8e43177d4 100644
--- a/Userland/Libraries/LibJS/Heap/Heap.h
+++ b/Userland/Libraries/LibJS/Heap/Heap.h
@@ -84,6 +84,7 @@ private:
     void gather_roots(HashTable<Cell*>&);
     void gather_conservative_roots(HashTable<Cell*>&);
     void mark_live_cells(HashTable<Cell*> const& live_cells);
+    void finalize_unmarked_cells();
     void sweep_dead_cells(bool print_report, Core::ElapsedTimer const&);
 
     CellAllocator& allocator_for_size(size_t);