diff --git a/core/fpdfdoc/BUILD.gn b/core/fpdfdoc/BUILD.gn
index c0478aa..9cc46ab 100644
--- a/core/fpdfdoc/BUILD.gn
+++ b/core/fpdfdoc/BUILD.gn
@@ -82,7 +82,6 @@
     "csection.h",
     "ctypeset.cpp",
     "ctypeset.h",
-    "ipdf_formnotify.h",
     "ipvt_fontmap.h",
   ]
   configs += [ "../../:pdfium_core_config" ]
diff --git a/core/fpdfdoc/cpdf_formcontrol.h b/core/fpdfdoc/cpdf_formcontrol.h
index d8e5e8c..d825634 100644
--- a/core/fpdfdoc/cpdf_formcontrol.h
+++ b/core/fpdfdoc/cpdf_formcontrol.h
@@ -15,7 +15,6 @@
 #include "core/fpdfdoc/cpdf_defaultappearance.h"
 #include "core/fpdfdoc/cpdf_formfield.h"
 #include "core/fpdfdoc/cpdf_iconfit.h"
-#include "core/fpdfdoc/ipdf_formnotify.h"
 #include "core/fxcrt/fx_coordinates.h"
 #include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/retain_ptr.h"
diff --git a/core/fpdfdoc/cpdf_interactiveform.cpp b/core/fpdfdoc/cpdf_interactiveform.cpp
index a7a4546..eeaac49 100644
--- a/core/fpdfdoc/cpdf_interactiveform.cpp
+++ b/core/fpdfdoc/cpdf_interactiveform.cpp
@@ -1088,6 +1088,6 @@
   return pDoc;
 }
 
-void CPDF_InteractiveForm::SetFormNotify(IPDF_FormNotify* pNotify) {
+void CPDF_InteractiveForm::SetNotifierIface(NotifierIface* pNotify) {
   m_pFormNotify = pNotify;
 }
diff --git a/core/fpdfdoc/cpdf_interactiveform.h b/core/fpdfdoc/cpdf_interactiveform.h
index 6d66f83..7d1f6c2 100644
--- a/core/fpdfdoc/cpdf_interactiveform.h
+++ b/core/fpdfdoc/cpdf_interactiveform.h
@@ -27,7 +27,6 @@
 class CPDF_FormControl;
 class CPDF_Object;
 class CPDF_Page;
-class IPDF_FormNotify;
 
 RetainPtr<CPDF_Font> AddNativeInteractiveFormFont(CPDF_Dictionary*& pFormDict,
                                                   CPDF_Document* pDocument,
@@ -35,6 +34,20 @@
 
 class CPDF_InteractiveForm {
  public:
+  class NotifierIface {
+   public:
+    virtual ~NotifierIface() = default;
+
+    virtual bool BeforeValueChange(CPDF_FormField* pField,
+                                   const WideString& csValue) = 0;
+    virtual void AfterValueChange(CPDF_FormField* pField) = 0;
+    virtual bool BeforeSelectionChange(CPDF_FormField* pField,
+                                       const WideString& csValue) = 0;
+    virtual void AfterSelectionChange(CPDF_FormField* pField) = 0;
+    virtual void AfterCheckedStatusChange(CPDF_FormField* pField) = 0;
+    virtual void AfterFormReset(CPDF_InteractiveForm* pForm) = 0;
+  };
+
   explicit CPDF_InteractiveForm(CPDF_Document* pDocument);
   ~CPDF_InteractiveForm();
 
@@ -85,11 +98,11 @@
                  bool bIncludeOrExclude,
                  NotificationOption notify);
 
-  void SetFormNotify(IPDF_FormNotify* pNotify);
+  void SetNotifierIface(NotifierIface* pNotify);
   bool HasXFAForm() const;
   void FixPageFields(CPDF_Page* pPage);
 
-  IPDF_FormNotify* GetFormNotify() const { return m_pFormNotify.Get(); }
+  NotifierIface* GetFormNotify() const { return m_pFormNotify.Get(); }
   CPDF_Document* GetDocument() const { return m_pDocument.Get(); }
   CPDF_Dictionary* GetFormDict() const { return m_pFormDict.Get(); }
 
@@ -113,7 +126,7 @@
   // Points into |m_ControlMap|.
   std::map<const CPDF_FormField*, std::vector<UnownedPtr<CPDF_FormControl>>>
       m_ControlLists;
-  UnownedPtr<IPDF_FormNotify> m_pFormNotify;
+  UnownedPtr<NotifierIface> m_pFormNotify;
 };
 
 #endif  // CORE_FPDFDOC_CPDF_INTERACTIVEFORM_H_
diff --git a/core/fpdfdoc/ipdf_formnotify.h b/core/fpdfdoc/ipdf_formnotify.h
deleted file mode 100644
index 6a72c68..0000000
--- a/core/fpdfdoc/ipdf_formnotify.h
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright 2016 PDFium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
-
-#ifndef CORE_FPDFDOC_IPDF_FORMNOTIFY_H_
-#define CORE_FPDFDOC_IPDF_FORMNOTIFY_H_
-
-#include "core/fxcrt/fx_string.h"
-
-class CPDF_FormField;
-class CPDF_InteractiveForm;
-
-class IPDF_FormNotify {
- public:
-  virtual ~IPDF_FormNotify() = default;
-
-  virtual bool BeforeValueChange(CPDF_FormField* pField,
-                                 const WideString& csValue) = 0;
-  virtual void AfterValueChange(CPDF_FormField* pField) = 0;
-
-  virtual bool BeforeSelectionChange(CPDF_FormField* pField,
-                                     const WideString& csValue) = 0;
-  virtual void AfterSelectionChange(CPDF_FormField* pField) = 0;
-
-  virtual void AfterCheckedStatusChange(CPDF_FormField* pField) = 0;
-  virtual void AfterFormReset(CPDF_InteractiveForm* pForm) = 0;
-};
-
-#endif  // CORE_FPDFDOC_IPDF_FORMNOTIFY_H_
diff --git a/fpdfsdk/cpdfsdk_interactiveform.cpp b/fpdfsdk/cpdfsdk_interactiveform.cpp
index 2f888b4..9e7c548 100644
--- a/fpdfsdk/cpdfsdk_interactiveform.cpp
+++ b/fpdfsdk/cpdfsdk_interactiveform.cpp
@@ -115,8 +115,7 @@
     : m_pFormFillEnv(pFormFillEnv),
       m_pInteractiveForm(pdfium::MakeUnique<CPDF_InteractiveForm>(
           m_pFormFillEnv->GetPDFDocument())) {
-  ASSERT(m_pFormFillEnv);
-  m_pInteractiveForm->SetFormNotify(this);
+  m_pInteractiveForm->SetNotifierIface(this);
   RemoveAllHighLights();
 }
 
diff --git a/fpdfsdk/cpdfsdk_interactiveform.h b/fpdfsdk/cpdfsdk_interactiveform.h
index ec76bee..df931d1 100644
--- a/fpdfsdk/cpdfsdk_interactiveform.h
+++ b/fpdfsdk/cpdfsdk_interactiveform.h
@@ -12,7 +12,7 @@
 #include <vector>
 
 #include "core/fpdfdoc/cpdf_action.h"
-#include "core/fpdfdoc/ipdf_formnotify.h"
+#include "core/fpdfdoc/cpdf_interactiveform.h"
 #include "core/fxcrt/unowned_ptr.h"
 #include "core/fxge/fx_dib.h"
 #include "fpdfsdk/cpdfsdk_widget.h"
@@ -21,11 +21,11 @@
 class CPDF_Dictionary;
 class CPDF_FormControl;
 class CPDF_FormField;
-class CPDF_InteractiveForm;
 class CPDF_Object;
 class CPDFSDK_FormFillEnvironment;
 
-class CPDFSDK_InteractiveForm final : public IPDF_FormNotify {
+class CPDFSDK_InteractiveForm final
+    : public CPDF_InteractiveForm::NotifierIface {
  public:
   explicit CPDFSDK_InteractiveForm(CPDFSDK_FormFillEnvironment* pFormFillEnv);
   ~CPDFSDK_InteractiveForm() override;
@@ -91,7 +91,7 @@
   FX_COLORREF GetHighlightColor(FormFieldType fieldType);
 
  private:
-  // IPDF_FormNotify:
+  // CPDF_InteractiveForm::NotifierIface:
   bool BeforeValueChange(CPDF_FormField* pField,
                          const WideString& csValue) override;
   void AfterValueChange(CPDF_FormField* pField) override;