diff --git a/cef_paths2.gypi b/cef_paths2.gypi
index 837d70071..0cf1e4475 100644
--- a/cef_paths2.gypi
+++ b/cef_paths2.gypi
@@ -245,6 +245,7 @@
       'tests/cefclient/browser/client_prefs.cc',
       'tests/cefclient/browser/client_prefs.h',
       'tests/cefclient/browser/client_types.h',
+      'tests/cefclient/browser/default_client_handler.cc',
       'tests/cefclient/browser/default_client_handler.h',
       'tests/cefclient/browser/dialog_test.cc',
       'tests/cefclient/browser/dialog_test.h',
diff --git a/tests/cefclient/browser/base_client_handler.cc b/tests/cefclient/browser/base_client_handler.cc
index 9832cce1d..49d93447c 100644
--- a/tests/cefclient/browser/base_client_handler.cc
+++ b/tests/cefclient/browser/base_client_handler.cc
@@ -14,7 +14,13 @@ BaseClientHandler::BaseClientHandler() {
 // static
 CefRefPtr<BaseClientHandler> BaseClientHandler::GetForBrowser(
     CefRefPtr<CefBrowser> browser) {
-  return static_cast<BaseClientHandler*>(browser->GetHost()->GetClient().get());
+  return GetForClient(browser->GetHost()->GetClient());
+}
+
+// static
+CefRefPtr<BaseClientHandler> BaseClientHandler::GetForClient(
+    CefRefPtr<CefClient> client) {
+  return static_cast<BaseClientHandler*>(client.get());
 }
 
 bool BaseClientHandler::OnProcessMessageReceived(
diff --git a/tests/cefclient/browser/base_client_handler.h b/tests/cefclient/browser/base_client_handler.h
index e811c03dc..6f5eba882 100644
--- a/tests/cefclient/browser/base_client_handler.h
+++ b/tests/cefclient/browser/base_client_handler.h
@@ -24,6 +24,9 @@ class BaseClientHandler : public CefClient,
   static CefRefPtr<BaseClientHandler> GetForBrowser(
       CefRefPtr<CefBrowser> browser);
 
+  // Returns the BaseClientHandler for |client|.
+  static CefRefPtr<BaseClientHandler> GetForClient(CefRefPtr<CefClient> client);
+
   // CefClient methods
   CefRefPtr<CefLifeSpanHandler> GetLifeSpanHandler() override { return this; }
   CefRefPtr<CefRequestHandler> GetRequestHandler() override { return this; }
@@ -92,6 +95,9 @@ class BaseClientHandler : public CefClient,
   void SetHangAction(HangAction action);
   HangAction GetHangAction() const;
 
+  // Used to determine the object type for each concrete implementation.
+  virtual const void* GetTypeKey() const = 0;
+
  protected:
   CefRefPtr<CefResourceManager> GetResourceManager() const {
     return resource_manager_;
diff --git a/tests/cefclient/browser/browser_window_osr_gtk.cc b/tests/cefclient/browser/browser_window_osr_gtk.cc
index aafbd8418..132f4fcd1 100644
--- a/tests/cefclient/browser/browser_window_osr_gtk.cc
+++ b/tests/cefclient/browser/browser_window_osr_gtk.cc
@@ -1124,7 +1124,9 @@ void BrowserWindowOsrGtk::OnBeforeClose(CefRefPtr<CefBrowser> browser) {
   CEF_REQUIRE_UI_THREAD();
 
   // Detach |this| from the ClientHandlerOsr.
-  static_cast<ClientHandlerOsr*>(client_handler_.get())->DetachOsrDelegate();
+  auto handler = ClientHandlerOsr::GetForClient(client_handler_);
+  CHECK(handler);
+  handler->DetachOsrDelegate();
 
   ScopedGdkThreadsEnter scoped_gdk_threads;
 
diff --git a/tests/cefclient/browser/browser_window_osr_mac.mm b/tests/cefclient/browser/browser_window_osr_mac.mm
index 511f0a1e1..dc0b7ac79 100644
--- a/tests/cefclient/browser/browser_window_osr_mac.mm
+++ b/tests/cefclient/browser/browser_window_osr_mac.mm
@@ -1581,8 +1581,10 @@ void BrowserWindowOsrMacImpl::OnBeforeClose(CefRefPtr<CefBrowser> browser) {
   REQUIRE_MAIN_THREAD();
 
   // Detach |this| from the ClientHandlerOsr.
-  static_cast<ClientHandlerOsr*>(browser_window_.client_handler_.get())
-      ->DetachOsrDelegate();
+  auto handler =
+      ClientHandlerOsr::GetForClient(browser_window_.client_handler_);
+  CHECK(handler);
+  handler->DetachOsrDelegate();
 }
 
 bool BrowserWindowOsrMacImpl::GetRootScreenRect(CefRefPtr<CefBrowser> browser,
diff --git a/tests/cefclient/browser/client_handler_osr.cc b/tests/cefclient/browser/client_handler_osr.cc
index 27e8125b8..667e22063 100644
--- a/tests/cefclient/browser/client_handler_osr.cc
+++ b/tests/cefclient/browser/client_handler_osr.cc
@@ -19,6 +19,16 @@ ClientHandlerOsr::ClientHandlerOsr(Delegate* delegate,
   DCHECK(osr_delegate_);
 }
 
+// static
+CefRefPtr<ClientHandlerOsr> ClientHandlerOsr::GetForClient(
+    CefRefPtr<CefClient> client) {
+  auto base = BaseClientHandler::GetForClient(client);
+  if (base && base->GetTypeKey() == &kTypeKey) {
+    return static_cast<ClientHandlerOsr*>(base.get());
+  }
+  return nullptr;
+}
+
 void ClientHandlerOsr::DetachOsrDelegate() {
   if (!CefCurrentlyOn(TID_UI)) {
     // Execute this method on the UI thread.
diff --git a/tests/cefclient/browser/client_handler_osr.h b/tests/cefclient/browser/client_handler_osr.h
index 8d748ea38..a8976873f 100644
--- a/tests/cefclient/browser/client_handler_osr.h
+++ b/tests/cefclient/browser/client_handler_osr.h
@@ -80,6 +80,10 @@ class ClientHandlerOsr : public ClientHandler,
                    bool with_controls,
                    const std::string& startup_url);
 
+  // Returns the ClientHandlerOsr for |client|, or nullptr if |client| is not a
+  // ClientHandlerOsr.
+  static CefRefPtr<ClientHandlerOsr> GetForClient(CefRefPtr<CefClient> client);
+
   // This object may outlive the OsrDelegate object so it's necessary for the
   // OsrDelegate to detach itself before destruction.
   void DetachOsrDelegate();
@@ -139,6 +143,10 @@ class ClientHandlerOsr : public ClientHandler,
   void OnAccessibilityLocationChange(CefRefPtr<CefValue> value) override;
 
  private:
+  // Used to determine the object type.
+  virtual const void* GetTypeKey() const override { return &kTypeKey; }
+  static const int kTypeKey = 0;
+
   // Only accessed on the UI thread.
   OsrDelegate* osr_delegate_;
 
diff --git a/tests/cefclient/browser/client_handler_std.cc b/tests/cefclient/browser/client_handler_std.cc
index e78166d93..a8dbc035b 100644
--- a/tests/cefclient/browser/client_handler_std.cc
+++ b/tests/cefclient/browser/client_handler_std.cc
@@ -11,4 +11,14 @@ ClientHandlerStd::ClientHandlerStd(Delegate* delegate,
                                    const std::string& startup_url)
     : ClientHandler(delegate, /*is_osr=*/false, with_controls, startup_url) {}
 
+// static
+CefRefPtr<ClientHandlerStd> ClientHandlerStd::GetForClient(
+    CefRefPtr<CefClient> client) {
+  auto base = BaseClientHandler::GetForClient(client);
+  if (base && base->GetTypeKey() == &kTypeKey) {
+    return static_cast<ClientHandlerStd*>(base.get());
+  }
+  return nullptr;
+}
+
 }  // namespace client
diff --git a/tests/cefclient/browser/client_handler_std.h b/tests/cefclient/browser/client_handler_std.h
index 02aa74767..f589824b3 100644
--- a/tests/cefclient/browser/client_handler_std.h
+++ b/tests/cefclient/browser/client_handler_std.h
@@ -18,7 +18,15 @@ class ClientHandlerStd : public ClientHandler {
                    bool with_controls,
                    const std::string& startup_url);
 
+  // Returns the ClientHandlerStd for |client|, or nullptr if |client| is not a
+  // ClientHandlerStd.
+  static CefRefPtr<ClientHandlerStd> GetForClient(CefRefPtr<CefClient> client);
+
  private:
+  // Used to determine the object type.
+  virtual const void* GetTypeKey() const override { return &kTypeKey; }
+  static const int kTypeKey = 0;
+
   // Include the default reference counting implementation.
   IMPLEMENT_REFCOUNTING(ClientHandlerStd);
   DISALLOW_COPY_AND_ASSIGN(ClientHandlerStd);
diff --git a/tests/cefclient/browser/default_client_handler.cc b/tests/cefclient/browser/default_client_handler.cc
new file mode 100644
index 000000000..21cc38c00
--- /dev/null
+++ b/tests/cefclient/browser/default_client_handler.cc
@@ -0,0 +1,19 @@
+// Copyright (c) 2024 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+
+#include "tests/cefclient/browser/default_client_handler.h"
+
+namespace client {
+
+// static
+CefRefPtr<DefaultClientHandler> DefaultClientHandler::GetForClient(
+    CefRefPtr<CefClient> client) {
+  auto base = BaseClientHandler::GetForClient(client);
+  if (base && base->GetTypeKey() == &kTypeKey) {
+    return static_cast<DefaultClientHandler*>(base.get());
+  }
+  return nullptr;
+}
+
+}  // namespace client
diff --git a/tests/cefclient/browser/default_client_handler.h b/tests/cefclient/browser/default_client_handler.h
index 678ac899a..371988b21 100644
--- a/tests/cefclient/browser/default_client_handler.h
+++ b/tests/cefclient/browser/default_client_handler.h
@@ -16,7 +16,16 @@ class DefaultClientHandler : public BaseClientHandler {
  public:
   DefaultClientHandler() = default;
 
+  // Returns the DefaultClientHandler for |client|, or nullptr if |client| is
+  // not a DefaultClientHandler.
+  static CefRefPtr<DefaultClientHandler> GetForClient(
+      CefRefPtr<CefClient> client);
+
  private:
+  // Used to determine the object type.
+  virtual const void* GetTypeKey() const override { return &kTypeKey; }
+  static const int kTypeKey = 0;
+
   IMPLEMENT_REFCOUNTING(DefaultClientHandler);
   DISALLOW_COPY_AND_ASSIGN(DefaultClientHandler);
 };
diff --git a/tests/cefclient/browser/osr_window_win.cc b/tests/cefclient/browser/osr_window_win.cc
index 38085e630..75db8fc4b 100644
--- a/tests/cefclient/browser/osr_window_win.cc
+++ b/tests/cefclient/browser/osr_window_win.cc
@@ -947,8 +947,10 @@ void OsrWindowWin::OnAfterCreated(CefRefPtr<CefBrowser> browser) {
 void OsrWindowWin::OnBeforeClose(CefRefPtr<CefBrowser> browser) {
   CEF_REQUIRE_UI_THREAD();
   // Detach |this| from the ClientHandlerOsr.
-  static_cast<ClientHandlerOsr*>(browser_->GetHost()->GetClient().get())
-      ->DetachOsrDelegate();
+  auto handler =
+      ClientHandlerOsr::GetForClient(browser_->GetHost()->GetClient());
+  CHECK(handler);
+  handler->DetachOsrDelegate();
   browser_ = nullptr;
   render_handler_->SetBrowser(nullptr);
   Destroy();
diff --git a/tests/cefclient/browser/root_window_views.cc b/tests/cefclient/browser/root_window_views.cc
index 276a78fa0..5a9f856ee 100644
--- a/tests/cefclient/browser/root_window_views.cc
+++ b/tests/cefclient/browser/root_window_views.cc
@@ -273,7 +273,12 @@ ViewsWindow::Delegate* RootWindowViews::GetDelegateForPopup(
     CefRefPtr<CefClient> client) {
   CEF_REQUIRE_UI_THREAD();
   // |handler| was created in RootWindowViews::InitAsPopup().
-  ClientHandlerStd* handler = static_cast<ClientHandlerStd*>(client.get());
+  // May return nullptr when running with `--use-default-popup`.
+  auto handler = ClientHandlerStd::GetForClient(client);
+  if (!handler) {
+    return nullptr;
+  }
+
   RootWindowViews* root_window =
       static_cast<RootWindowViews*>(handler->delegate());