diff --git a/fpdfsdk/cpdfsdk_annot.cpp b/fpdfsdk/cpdfsdk_annot.cpp
index 36bec15..9f8cf25 100644
--- a/fpdfsdk/cpdfsdk_annot.cpp
+++ b/fpdfsdk/cpdfsdk_annot.cpp
@@ -9,6 +9,7 @@
 #include <algorithm>
 
 #include "fpdfsdk/include/fsdk_mgr.h"
+#include "third_party/base/stl_util.h"
 
 #ifdef PDF_ENABLE_XFA
 #include "fpdfsdk/fpdfxfa/include/fpdfxfa_doc.h"
@@ -21,10 +22,39 @@
 
 }  // namespace
 
+CPDFSDK_Annot::Observer::Observer(CPDFSDK_Annot** pWatchedPtr)
+    : m_pWatchedPtr(pWatchedPtr) {
+  (*m_pWatchedPtr)->AddObserver(this);
+}
+
+CPDFSDK_Annot::Observer::~Observer() {
+  if (m_pWatchedPtr)
+    (*m_pWatchedPtr)->RemoveObserver(this);
+}
+
+void CPDFSDK_Annot::Observer::OnAnnotDestroyed() {
+  ASSERT(m_pWatchedPtr);
+  *m_pWatchedPtr = nullptr;
+  m_pWatchedPtr = nullptr;
+}
+
 CPDFSDK_Annot::CPDFSDK_Annot(CPDFSDK_PageView* pPageView)
     : m_pPageView(pPageView), m_bSelected(FALSE) {}
 
-CPDFSDK_Annot::~CPDFSDK_Annot() {}
+CPDFSDK_Annot::~CPDFSDK_Annot() {
+  for (auto* pObserver : m_Observers)
+    pObserver->OnAnnotDestroyed();
+}
+
+void CPDFSDK_Annot::AddObserver(Observer* pObserver) {
+  ASSERT(!pdfium::ContainsKey(m_Observers, pObserver));
+  m_Observers.insert(pObserver);
+}
+
+void CPDFSDK_Annot::RemoveObserver(Observer* pObserver) {
+  ASSERT(pdfium::ContainsKey(m_Observers, pObserver));
+  m_Observers.erase(pObserver);
+}
 
 #ifdef PDF_ENABLE_XFA
 
diff --git a/fpdfsdk/cpdfsdk_widget.cpp b/fpdfsdk/cpdfsdk_widget.cpp
index dcccf0c..4cd9391 100644
--- a/fpdfsdk/cpdfsdk_widget.cpp
+++ b/fpdfsdk/cpdfsdk_widget.cpp
@@ -26,7 +26,6 @@
 #include "fpdfsdk/include/fsdk_mgr.h"
 #include "fpdfsdk/pdfwindow/PWL_Edit.h"
 #include "fpdfsdk/pdfwindow/PWL_Utils.h"
-#include "third_party/base/stl_util.h"
 
 #ifdef PDF_ENABLE_XFA
 #include "fpdfsdk/fpdfxfa/include/fpdfxfa_doc.h"
@@ -37,22 +36,6 @@
 #include "xfa/fxfa/include/xfa_ffwidgethandler.h"
 #endif  // PDF_ENABLE_XFA
 
-CPDFSDK_Widget::Observer::Observer(CPDFSDK_Widget** pWatchedPtr)
-    : m_pWatchedPtr(pWatchedPtr) {
-  (*m_pWatchedPtr)->AddObserver(this);
-}
-
-CPDFSDK_Widget::Observer::~Observer() {
-  if (m_pWatchedPtr)
-    (*m_pWatchedPtr)->RemoveObserver(this);
-}
-
-void CPDFSDK_Widget::Observer::OnWidgetDestroyed() {
-  ASSERT(m_pWatchedPtr);
-  *m_pWatchedPtr = nullptr;
-  m_pWatchedPtr = nullptr;
-}
-
 CPDFSDK_Widget::CPDFSDK_Widget(CPDF_Annot* pAnnot,
                                CPDFSDK_PageView* pPageView,
                                CPDFSDK_InterForm* pInterForm)
@@ -68,20 +51,7 @@
 {
 }
 
-CPDFSDK_Widget::~CPDFSDK_Widget() {
-  for (auto* pObserver : m_Observers)
-    pObserver->OnWidgetDestroyed();
-}
-
-void CPDFSDK_Widget::AddObserver(Observer* pObserver) {
-  ASSERT(!pdfium::ContainsKey(m_Observers, pObserver));
-  m_Observers.insert(pObserver);
-}
-
-void CPDFSDK_Widget::RemoveObserver(Observer* pObserver) {
-  ASSERT(pdfium::ContainsKey(m_Observers, pObserver));
-  m_Observers.erase(pObserver);
-}
+CPDFSDK_Widget::~CPDFSDK_Widget() {}
 
 #ifdef PDF_ENABLE_XFA
 CXFA_FFWidget* CPDFSDK_Widget::GetMixXFAWidget() const {
diff --git a/fpdfsdk/include/cpdfsdk_annot.h b/fpdfsdk/include/cpdfsdk_annot.h
index 0fbee9e..15f662c 100644
--- a/fpdfsdk/include/cpdfsdk_annot.h
+++ b/fpdfsdk/include/cpdfsdk_annot.h
@@ -23,9 +23,22 @@
 
 class CPDFSDK_Annot {
  public:
+  class Observer {
+   public:
+    explicit Observer(CPDFSDK_Annot** pWatchedPtr);
+    ~Observer();
+    void OnAnnotDestroyed();
+
+   private:
+    CPDFSDK_Annot** m_pWatchedPtr;
+  };
+
   explicit CPDFSDK_Annot(CPDFSDK_PageView* pPageView);
   virtual ~CPDFSDK_Annot();
 
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
 #ifdef PDF_ENABLE_XFA
   virtual FX_BOOL IsXFAField();
   virtual CXFA_FFWidget* GetXFAWidget() const;
@@ -57,6 +70,7 @@
   void SetSelected(FX_BOOL bSelected);
 
  protected:
+  std::set<Observer*> m_Observers;
   CPDFSDK_PageView* m_pPageView;
   FX_BOOL m_bSelected;
 };
diff --git a/fpdfsdk/include/cpdfsdk_widget.h b/fpdfsdk/include/cpdfsdk_widget.h
index 7f5e345..201de2d 100644
--- a/fpdfsdk/include/cpdfsdk_widget.h
+++ b/fpdfsdk/include/cpdfsdk_widget.h
@@ -35,17 +35,6 @@
 
 class CPDFSDK_Widget : public CPDFSDK_BAAnnot {
  public:
-  class Observer {
-   public:
-    explicit Observer(CPDFSDK_Widget** pWatchedPtr);
-    ~Observer();
-
-    void OnWidgetDestroyed();
-
-   private:
-    CPDFSDK_Widget** m_pWatchedPtr;
-  };
-
 #ifdef PDF_ENABLE_XFA
   CXFA_FFWidget* GetMixXFAWidget() const;
   CXFA_FFWidget* GetGroupMixXFAWidget();
@@ -75,9 +64,6 @@
                  CPDFSDK_InterForm* pInterForm);
   ~CPDFSDK_Widget() override;
 
-  void AddObserver(Observer* observer);
-  void RemoveObserver(Observer* observer);
-
   CFX_ByteString GetSubType() const override;
   CPDF_Action GetAAction(CPDF_AAction::AActionType eAAT) override;
   FX_BOOL IsAppearanceValid() override;
@@ -180,7 +166,6 @@
   FX_BOOL m_bAppModified;
   int32_t m_nAppAge;
   int32_t m_nValueAge;
-  std::set<Observer*> m_Observers;
 
 #ifdef PDF_ENABLE_XFA
   mutable CXFA_FFWidget* m_hMixXFAWidget;
diff --git a/fpdfsdk/javascript/Annot.cpp b/fpdfsdk/javascript/Annot.cpp
index df12327..95a428a 100644
--- a/fpdfsdk/javascript/Annot.cpp
+++ b/fpdfsdk/javascript/Annot.cpp
@@ -11,6 +11,14 @@
 #include "fpdfsdk/javascript/JS_Value.h"
 #include "fpdfsdk/javascript/cjs_context.h"
 
+namespace {
+
+CPDFSDK_BAAnnot* ToBAAnnot(CPDFSDK_Annot* annot) {
+  return static_cast<CPDFSDK_BAAnnot*>(annot);
+}
+
+}  // namespace
+
 BEGIN_JS_STATIC_CONST(CJS_Annot)
 END_JS_STATIC_CONST()
 
@@ -32,8 +40,12 @@
 FX_BOOL Annot::hidden(IJS_Context* cc,
                       CJS_PropValue& vp,
                       CFX_WideString& sError) {
+  CPDFSDK_BAAnnot* baAnnot = ToBAAnnot(m_pAnnot);
+  if (!baAnnot)
+    return FALSE;
+
   if (vp.IsGetting()) {
-    CPDF_Annot* pPDFAnnot = m_BAAnnot->GetPDFAnnot();
+    CPDF_Annot* pPDFAnnot = baAnnot->GetPDFAnnot();
     vp << CPDF_Annot::IsAnnotationHidden(pPDFAnnot->GetAnnotDict());
     return TRUE;
   }
@@ -41,7 +53,7 @@
   bool bHidden;
   vp >> bHidden;
 
-  uint32_t flags = m_BAAnnot->GetFlags();
+  uint32_t flags = baAnnot->GetFlags();
   if (bHidden) {
     flags |= ANNOTFLAG_HIDDEN;
     flags |= ANNOTFLAG_INVISIBLE;
@@ -53,21 +65,25 @@
     flags &= ~ANNOTFLAG_NOVIEW;
     flags |= ANNOTFLAG_PRINT;
   }
-  m_BAAnnot->SetFlags(flags);
+  baAnnot->SetFlags(flags);
   return TRUE;
 }
 
 FX_BOOL Annot::name(IJS_Context* cc,
                     CJS_PropValue& vp,
                     CFX_WideString& sError) {
+  CPDFSDK_BAAnnot* baAnnot = ToBAAnnot(m_pAnnot);
+  if (!baAnnot)
+    return FALSE;
+
   if (vp.IsGetting()) {
-    vp << m_BAAnnot->GetAnnotName();
+    vp << baAnnot->GetAnnotName();
     return TRUE;
   }
 
   CFX_WideString annotName;
   vp >> annotName;
-  m_BAAnnot->SetAnnotName(annotName);
+  baAnnot->SetAnnotName(annotName);
   return TRUE;
 }
 
@@ -80,10 +96,15 @@
     return FALSE;
   }
 
-  vp << m_BAAnnot->GetType();
+  CPDFSDK_BAAnnot* baAnnot = ToBAAnnot(m_pAnnot);
+  if (!baAnnot)
+    return FALSE;
+
+  vp << baAnnot->GetType();
   return TRUE;
 }
 
 void Annot::SetSDKAnnot(CPDFSDK_BAAnnot* annot) {
-  m_BAAnnot = annot;
+  m_pAnnot = annot;
+  m_pObserver.reset(new CPDFSDK_Annot::Observer(&m_pAnnot));
 }
diff --git a/fpdfsdk/javascript/Annot.h b/fpdfsdk/javascript/Annot.h
index b3ea292..be85035 100644
--- a/fpdfsdk/javascript/Annot.h
+++ b/fpdfsdk/javascript/Annot.h
@@ -7,6 +7,8 @@
 #ifndef FPDFSDK_JAVASCRIPT_ANNOT_H_
 #define FPDFSDK_JAVASCRIPT_ANNOT_H_
 
+#include <memory>
+
 #include "fpdfsdk/include/cpdfsdk_baannot.h"
 #include "fpdfsdk/javascript/JS_Define.h"
 
@@ -22,7 +24,8 @@
   void SetSDKAnnot(CPDFSDK_BAAnnot* annot);
 
  private:
-  CPDFSDK_BAAnnot* m_BAAnnot = nullptr;
+  CPDFSDK_Annot* m_pAnnot = nullptr;
+  std::unique_ptr<CPDFSDK_Annot::Observer> m_pObserver;
 };
 
 class CJS_Annot : public CJS_Object {
diff --git a/fpdfsdk/javascript/Field.cpp b/fpdfsdk/javascript/Field.cpp
index 0a184d8..64c7735 100644
--- a/fpdfsdk/javascript/Field.cpp
+++ b/fpdfsdk/javascript/Field.cpp
@@ -268,11 +268,12 @@
 
     int nFieldType = pFormField->GetFieldType();
     if (nFieldType == FIELDTYPE_COMBOBOX || nFieldType == FIELDTYPE_TEXTFIELD) {
-      for (CPDFSDK_Widget* pWidget : widgets) {
+      for (CPDFSDK_Annot* pAnnot : widgets) {
         FX_BOOL bFormatted = FALSE;
-        CPDFSDK_Widget::Observer observer(&pWidget);
+        CPDFSDK_Widget* pWidget = static_cast<CPDFSDK_Widget*>(pAnnot);
+        CPDFSDK_Widget::Observer observer(&pAnnot);
         CFX_WideString sValue = pWidget->OnFormat(bFormatted);
-        if (pWidget) {
+        if (pAnnot) {
           pWidget->ResetAppearance(bFormatted ? sValue.c_str() : nullptr,
                                    FALSE);
         }