diff --git a/src/google/protobuf/lazy_field_heavy.cc b/src/google/protobuf/lazy_field_heavy.cc
deleted file mode 100644
index 02d4d2ebfb..0000000000
--- a/src/google/protobuf/lazy_field_heavy.cc
+++ /dev/null
@@ -1,105 +0,0 @@
-// Protocol Buffers - Google's data interchange format
-// Copyright 2023 Google Inc.  All rights reserved.
-// https://developers.google.com/protocol-buffers/
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-#include "google/protobuf/lazy_field.h"
-#include "google/protobuf/message.h"
-
-namespace google {
-namespace protobuf {
-namespace internal {
-namespace {
-class ByFactory {
- public:
-  explicit ByFactory(const Descriptor* type, MessageFactory* factory)
-      : type_(type), factory_(factory) {}
-
-  Message* New(Arena* arena) const {
-    return factory_->GetPrototype(type_)->New(arena);
-  }
-
-  const Message& Default() const { return *factory_->GetPrototype(type_); }
-
- private:
-  const Descriptor* type_;
-  MessageFactory* factory_;
-};
-
-}  // namespace
-
-const Message& LazyField::GetDynamic(const Descriptor* type,
-                                     MessageFactory* factory,
-                                     Arena* arena) const {
-  return DownCast<const Message&>(GetGeneric(ByFactory(type, factory), arena));
-}
-
-Message* LazyField::MutableDynamic(const Descriptor* type,
-                                   MessageFactory* factory, Arena* arena) {
-  return DownCast<Message*>(
-      MutableGeneric(ByFactory(type, factory), arena, nullptr));
-}
-
-Message* LazyField::ReleaseDynamic(const Descriptor* type,
-                                   MessageFactory* factory, Arena* arena) {
-  return DownCast<Message*>(ReleaseGeneric(ByFactory(type, factory), arena));
-}
-
-Message* LazyField::UnsafeArenaReleaseDynamic(const Descriptor* type,
-                                              MessageFactory* factory,
-                                              Arena* arena) {
-  return DownCast<Message*>(
-      UnsafeArenaReleaseGeneric(ByFactory(type, factory), arena));
-}
-
-size_t LazyField::SpaceUsedExcludingSelfLong() const {
-  // absl::Cord::EstimatedMemoryUsage counts itself that should be excluded
-  // because sizeof(Cord) is already counted in self.
-  size_t total_size = unparsed_.EstimatedMemoryUsage() - sizeof(absl::Cord);
-  switch (GetLogicalState()) {
-    case LogicalState::kClearExposed:
-    case LogicalState::kNoParseRequired:
-    case LogicalState::kDirty:
-    case LogicalState::kParseError: {
-      const auto* message = raw_.load(std::memory_order_relaxed).message();
-      total_size += DownCast<const Message*>(message)->SpaceUsedLong();
-    } break;
-    case LogicalState::kClear:
-    case LogicalState::kParseRequired:
-      // We may have a `Message*` here, but we cannot safely access it
-      // because, a racing SharedInit could delete it out from under us.
-      // Other states in this structure are already passed kSharedInit and are
-      // thus safe.
-      break;  // Nothing to add.
-  }
-  return total_size;
-}
-
-}  // namespace internal
-}  // namespace protobuf
-}  // namespace google