diff --git a/xfa/fde/cfde_texteditengine.h b/xfa/fde/cfde_texteditengine.h
index 9cd8387..4d9c0c8 100644
--- a/xfa/fde/cfde_texteditengine.h
+++ b/xfa/fde/cfde_texteditengine.h
@@ -38,7 +38,7 @@
     default;
 inline FDE_TEXTEDITPIECE::~FDE_TEXTEDITPIECE() = default;
 
-class CFDE_TextEditEngine : public CFGAS_TxtBreak::Engine {
+class CFDE_TextEditEngine final : public CFGAS_TxtBreak::Engine {
  public:
   class Iterator {
    public:
diff --git a/xfa/fxfa/cxfa_ffapp.h b/xfa/fxfa/cxfa_ffapp.h
index f3a5c75..d26b90c 100644
--- a/xfa/fxfa/cxfa_ffapp.h
+++ b/xfa/fxfa/cxfa_ffapp.h
@@ -21,8 +21,8 @@
 class CXFA_FontMgr;
 class IFX_SeekableReadStream;
 
-class CXFA_FFApp : public cppgc::GarbageCollected<CXFA_FFApp>,
-                   public CFWL_App::AdapterIface {
+class CXFA_FFApp final : public cppgc::GarbageCollected<CXFA_FFApp>,
+                         public CFWL_App::AdapterIface {
  public:
   class CallbackIface {
    public:
diff --git a/xfa/fxfa/cxfa_fwladapterwidgetmgr.h b/xfa/fxfa/cxfa_fwladapterwidgetmgr.h
index c3f97dd..c300c35 100644
--- a/xfa/fxfa/cxfa_fwladapterwidgetmgr.h
+++ b/xfa/fxfa/cxfa_fwladapterwidgetmgr.h
@@ -14,7 +14,7 @@
 class CFWL_Widget;
 class CFX_RectF;
 
-class CXFA_FWLAdapterWidgetMgr
+class CXFA_FWLAdapterWidgetMgr final
     : public cppgc::GarbageCollected<CXFA_FWLAdapterWidgetMgr>,
       public CFWL_WidgetMgr::AdapterIface {
  public:
diff --git a/xfa/fxfa/layout/cxfa_layoutprocessor.h b/xfa/fxfa/layout/cxfa_layoutprocessor.h
index 8edefb6..21a8b06 100644
--- a/xfa/fxfa/layout/cxfa_layoutprocessor.h
+++ b/xfa/fxfa/layout/cxfa_layoutprocessor.h
@@ -28,7 +28,7 @@
 class Heap;
 }  // namespace cppgc
 
-class CXFA_LayoutProcessor : public CXFA_Document::LayoutProcessorIface {
+class CXFA_LayoutProcessor final : public CXFA_Document::LayoutProcessorIface {
  public:
   static CXFA_LayoutProcessor* FromDocument(const CXFA_Document* pXFADoc);
 
diff --git a/xfa/fxfa/parser/cxfa_localemgr.h b/xfa/fxfa/parser/cxfa_localemgr.h
index ce739e6..051bfe4 100644
--- a/xfa/fxfa/parser/cxfa_localemgr.h
+++ b/xfa/fxfa/parser/cxfa_localemgr.h
@@ -22,8 +22,8 @@
 class CXFA_NodeLocale;
 class CXFA_XMLLocale;
 
-class CXFA_LocaleMgr : public cppgc::GarbageCollected<CXFA_LocaleMgr>,
-                       public LocaleMgrIface {
+class CXFA_LocaleMgr final : public cppgc::GarbageCollected<CXFA_LocaleMgr>,
+                             public LocaleMgrIface {
  public:
   enum class LangID : uint16_t {
     k_zh_HK = 0x0c04,