diff --git a/src/corelib/CMakeLists.txt b/src/corelib/CMakeLists.txt
index 38cca5a9682..c9599cb1bc0 100644
--- a/src/corelib/CMakeLists.txt
+++ b/src/corelib/CMakeLists.txt
@@ -204,7 +204,7 @@ qt_internal_add_module(Core
         serialization/qcbormap.h
         serialization/qcborstream.h
         serialization/qcborvalue.cpp serialization/qcborvalue.h serialization/qcborvalue_p.h
-        serialization/qdatastream.cpp serialization/qdatastream.h serialization/qdatastream_p.h
+        serialization/qdatastream.cpp serialization/qdatastream.h
         serialization/qjson_p.h
         serialization/qjsonarray.cpp serialization/qjsonarray.h
         serialization/qjsoncbor.cpp
diff --git a/src/corelib/serialization/qdatastream.cpp b/src/corelib/serialization/qdatastream.cpp
index 4a18c6b781e..8abcd239945 100644
--- a/src/corelib/serialization/qdatastream.cpp
+++ b/src/corelib/serialization/qdatastream.cpp
@@ -2,7 +2,6 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
 #include "qdatastream.h"
-#include "qdatastream_p.h"
 
 #if !defined(QT_NO_DATASTREAM) || defined(QT_BOOTSTRAPPED)
 #include "qbuffer.h"
diff --git a/src/corelib/serialization/qdatastream.h b/src/corelib/serialization/qdatastream.h
index 9be7e2e95a2..7023940ead8 100644
--- a/src/corelib/serialization/qdatastream.h
+++ b/src/corelib/serialization/qdatastream.h
@@ -29,7 +29,6 @@ class QIODevice;
 class QString;
 
 #if !defined(QT_NO_DATASTREAM)
-class QDataStreamPrivate;
 namespace QtPrivate {
 class StreamStateSaver;
 template <typename Container>
@@ -219,7 +218,9 @@ public:
 private:
     Q_DISABLE_COPY(QDataStream)
 
-    std::unique_ptr<QDataStreamPrivate> d;
+#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
+    void* const d = nullptr;
+#endif
 
     QIODevice *dev = nullptr;
     bool owndev = false;
diff --git a/src/corelib/serialization/qdatastream_p.h b/src/corelib/serialization/qdatastream_p.h
deleted file mode 100644
index c4fe7c784cf..00000000000
--- a/src/corelib/serialization/qdatastream_p.h
+++ /dev/null
@@ -1,32 +0,0 @@
-// Copyright (C) 2016 The Qt Company Ltd.
-// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
-
-#ifndef QDATASTREAM_P_H
-#define QDATASTREAM_P_H
-
-//
-//  W A R N I N G
-//  -------------
-//
-// This file is not part of the Qt API.  It exists purely as an
-// implementation detail.  This header file may change from version to
-// version without notice, or even be removed.
-//
-// We mean it.
-//
-
-#include <QtCore/private/qglobal_p.h>
-#include <qdatastream.h>
-
-QT_BEGIN_NAMESPACE
-
-#if !defined(QT_NO_DATASTREAM) || defined(QT_BOOTSTRAPPED)
-class QDataStreamPrivate
-{
-public:
-};
-#endif
-
-QT_END_NAMESPACE
-
-#endif // QDATASTREAM_P_H