diff --git a/xfa/fwl/cfwl_caret.cpp b/xfa/fwl/cfwl_caret.cpp
index 8aef853f6..665504b13 100644
--- a/xfa/fwl/cfwl_caret.cpp
+++ b/xfa/fwl/cfwl_caret.cpp
@@ -32,6 +32,15 @@ CFWL_Caret::CFWL_Caret(CFWL_App* app,
 
 CFWL_Caret::~CFWL_Caret() = default;
 
+void CFWL_Caret::PreFinalize() {
+  // Deregister the embedder timer at PreFinalize time, not in the destructor.
+  // The cppgc heap sweeps incrementally, so the destructor may run long after
+  // this object's payload (and that of `outer_`) has been poisoned/reclaimed,
+  // letting an embedder timer fire OnTimerFired() on a dead widget.
+  timer_.reset();
+  CFWL_Widget::PreFinalize();
+}
+
 FWL_Type CFWL_Caret::GetClassID() const {
   return FWL_Type::Caret;
 }
diff --git a/xfa/fwl/cfwl_caret.h b/xfa/fwl/cfwl_caret.h
index e2626ed40..939515456 100644
--- a/xfa/fwl/cfwl_caret.h
+++ b/xfa/fwl/cfwl_caret.h
@@ -21,6 +21,7 @@ class CFWL_Caret final : public CFWL_Widget, public CFX_Timer::CallbackIface {
   ~CFWL_Caret() override;
 
   // CFWL_Widget:
+  void PreFinalize() override;
   FWL_Type GetClassID() const override;
   void DrawWidget(CFGAS_GEGraphics* pGraphics,
                   const CFX_Matrix& matrix) override;
diff --git a/xfa/fwl/cfwl_scrollbar.cpp b/xfa/fwl/cfwl_scrollbar.cpp
index bb8145d94..4c0ba4ef9 100644
--- a/xfa/fwl/cfwl_scrollbar.cpp
+++ b/xfa/fwl/cfwl_scrollbar.cpp
@@ -34,6 +34,15 @@ CFWL_ScrollBar::CFWL_ScrollBar(CFWL_App* app,
 
 CFWL_ScrollBar::~CFWL_ScrollBar() = default;
 
+void CFWL_ScrollBar::PreFinalize() {
+  // Deregister the embedder timer at PreFinalize time, not in the destructor.
+  // The cppgc heap sweeps incrementally, so the destructor may run long after
+  // this object's payload (and that of `outer_`) has been poisoned/reclaimed,
+  // letting an embedder timer fire OnTimerFired() on a dead widget.
+  timer_.reset();
+  CFWL_Widget::PreFinalize();
+}
+
 FWL_Type CFWL_ScrollBar::GetClassID() const {
   return FWL_Type::ScrollBar;
 }
diff --git a/xfa/fwl/cfwl_scrollbar.h b/xfa/fwl/cfwl_scrollbar.h
index 41d71374d..b01d78973 100644
--- a/xfa/fwl/cfwl_scrollbar.h
+++ b/xfa/fwl/cfwl_scrollbar.h
@@ -29,6 +29,7 @@ class CFWL_ScrollBar final : public CFWL_Widget,
   ~CFWL_ScrollBar() override;
 
   // CFWL_Widget:
+  void PreFinalize() override;
   FWL_Type GetClassID() const override;
   void Update() override;
   void DrawWidget(CFGAS_GEGraphics* pGraphics,