diff --git a/src/corelib/compat/removed_api.cpp b/src/corelib/compat/removed_api.cpp
index abfb11c8724..16c44f09a3c 100644
--- a/src/corelib/compat/removed_api.cpp
+++ b/src/corelib/compat/removed_api.cpp
@@ -708,9 +708,9 @@ bool QDateTime::precedes(const QDateTime &other) const
 
 QDataStream &QDataStream::readBytes(char *&s, uint &l)
 {
-    qsizetype length = 0;
+    qint64 length = 0;
     (void)readBytes(s, length);
-    if (length != qsizetype(uint(length))) {
+    if (length != qint64(uint(length))) {
         setStatus(ReadCorruptData); // Cannot store length in l
         delete[] s;
         l = 0;
@@ -722,12 +722,7 @@ QDataStream &QDataStream::readBytes(char *&s, uint &l)
 
 QDataStream &QDataStream::writeBytes(const char *s, uint len)
 {
-    qsizetype length = qsizetype(len);
-    if (length < 0) {
-        setStatus(WriteFailed);
-        return *this;
-    }
-    return writeBytes(s, length);
+    return writeBytes(s, qint64(len));
 }
 
 int QDataStream::skipRawData(int len)
@@ -735,25 +730,21 @@ int QDataStream::skipRawData(int len)
     return int(skipRawData(qint64(len)));
 }
 
-#if QT_POINTER_SIZE != 4
-
 int QDataStream::readBlock(char *data, int len)
 {
-    return int(readBlock(data, qsizetype(len)));
+    return int(readBlock(data, qint64(len)));
 }
 
 int QDataStream::readRawData(char *s, int len)
 {
-    return int(readRawData(s, qsizetype(len)));
+    return int(readRawData(s, qint64(len)));
 }
 
 int QDataStream::writeRawData(const char *s, int len)
 {
-    return writeRawData(s, qsizetype(len));
+    return writeRawData(s, qint64(len));
 }
 
-#endif // QT_POINTER_SIZE != 4
-
 #if defined(Q_OS_ANDROID)
 
 #include "qjniobject.h"
diff --git a/src/corelib/serialization/qdatastream.cpp b/src/corelib/serialization/qdatastream.cpp
index 008edc088a0..d67908bb2cd 100644
--- a/src/corelib/serialization/qdatastream.cpp
+++ b/src/corelib/serialization/qdatastream.cpp
@@ -757,13 +757,13 @@ bool QDataStream::isDeviceTransactionStarted() const
     \internal
 */
 
-qsizetype QDataStream::readBlock(char *data, qsizetype len)
+qint64 QDataStream::readBlock(char *data, qint64 len)
 {
     // Disable reads on failure in transacted stream
     if (q_status != Ok && dev->isTransactionStarted())
         return -1;
 
-    const qsizetype readResult = dev->read(data, len);
+    const qint64 readResult = dev->read(data, len);
     if (readResult != len)
         setStatus(ReadPastEnd);
     return readResult;
@@ -1002,7 +1002,7 @@ QDataStream &QDataStream::operator>>(double &f)
 
 QDataStream &QDataStream::operator>>(char *&s)
 {
-    qsizetype len = 0;
+    qint64 len = 0;
     return readBytes(s, len);
 }
 
@@ -1057,7 +1057,7 @@ QDataStream &QDataStream::operator>>(char32_t &c)
     \sa readRawData(), writeBytes()
 */
 
-QDataStream &QDataStream::readBytes(char *&s, qsizetype &l)
+QDataStream &QDataStream::readBytes(char *&s, qint64 &l)
 {
     s = nullptr;
     l = 0;
@@ -1069,7 +1069,7 @@ QDataStream &QDataStream::readBytes(char *&s, qsizetype &l)
 
     qsizetype len = qsizetype(length);
     if (length != len || length < 0) {
-        setStatus(SizeLimitExceeded); // Cannot store len in l
+        setStatus(SizeLimitExceeded); // Cannot store len
         return *this;
     }
 
@@ -1108,7 +1108,7 @@ QDataStream &QDataStream::readBytes(char *&s, qsizetype &l)
     \sa readBytes(), QIODevice::read(), writeRawData()
 */
 
-qsizetype QDataStream::readRawData(char *s, qsizetype len)
+qint64 QDataStream::readRawData(char *s, qint64 len)
 {
     CHECK_STREAM_PRECOND(-1)
     return readBlock(s, len);
@@ -1389,7 +1389,7 @@ QDataStream &QDataStream::operator<<(char32_t c)
     \sa writeRawData(), readBytes()
 */
 
-QDataStream &QDataStream::writeBytes(const char *s, qsizetype len)
+QDataStream &QDataStream::writeBytes(const char *s, qint64 len)
 {
     if (len < 0) {
         q_status = WriteFailed;
@@ -1410,10 +1410,10 @@ QDataStream &QDataStream::writeBytes(const char *s, qsizetype len)
     \sa writeBytes(), QIODevice::write(), readRawData()
 */
 
-qsizetype QDataStream::writeRawData(const char *s, qsizetype len)
+qint64 QDataStream::writeRawData(const char *s, qint64 len)
 {
     CHECK_STREAM_WRITE_PRECOND(-1)
-    qsizetype ret = dev->write(s, len);
+    qint64 ret = dev->write(s, len);
     if (ret != len)
         q_status = WriteFailed;
     return ret;
diff --git a/src/corelib/serialization/qdatastream.h b/src/corelib/serialization/qdatastream.h
index 6c67753ecda..80f4b234539 100644
--- a/src/corelib/serialization/qdatastream.h
+++ b/src/corelib/serialization/qdatastream.h
@@ -180,15 +180,13 @@ public:
     QDataStream &readBytes(char *&, uint &len);
     QDataStream &writeBytes(const char *, uint len);
     int skipRawData(int len);
-#endif
-#if QT_CORE_REMOVED_SINCE(6, 7) && QT_POINTER_SIZE != 4
     int readRawData(char *, int len);
     int writeRawData(const char *, int len);
 #endif
-    QDataStream &readBytes(char *&, qsizetype &len);
-    qsizetype readRawData(char *, qsizetype len);
-    QDataStream &writeBytes(const char *, qsizetype len);
-    qsizetype writeRawData(const char *, qsizetype len);
+    QDataStream &readBytes(char *&, qint64 &len);
+    qint64 readRawData(char *, qint64 len);
+    QDataStream &writeBytes(const char *, qint64 len);
+    qint64 writeRawData(const char *, qint64 len);
     qint64 skipRawData(qint64 len);
 
     void startTransaction();
@@ -208,10 +206,10 @@ private:
     ByteOrder byteorder;
     int ver;
     Status q_status;
-#if QT_CORE_REMOVED_SINCE(6, 7) && QT_POINTER_SIZE != 4
+#if QT_CORE_REMOVED_SINCE(6, 7)
     int readBlock(char *data, int len);
 #endif
-    qsizetype readBlock(char *data, qsizetype len);
+    qint64 readBlock(char *data, qint64 len);
     static inline qint64 readQSizeType(QDataStream &s);
     static inline void writeQSizeType(QDataStream &s, qint64 value);
     enum class QDataStreamSizes : quint32 { NullCode = 0xffffffffu, ExtendedSize = 0xfffffffeu };
diff --git a/tests/auto/corelib/serialization/qdatastream/tst_qdatastream.cpp b/tests/auto/corelib/serialization/qdatastream/tst_qdatastream.cpp
index c6d9d5d4abd..09f2bbc860f 100644
--- a/tests/auto/corelib/serialization/qdatastream/tst_qdatastream.cpp
+++ b/tests/auto/corelib/serialization/qdatastream/tst_qdatastream.cpp
@@ -2818,10 +2818,10 @@ void tst_QDataStream::status_charptr_QByteArray()
     {
         QDataStream stream(&data, QIODevice::ReadOnly);
         char *buf;
-        qsizetype len;
+        qint64 len;
         stream.readBytes(buf, len);
 
-        QCOMPARE(len, expectedString.size());
+        QCOMPARE(len, qint64(expectedString.size()));
         QCOMPARE(QByteArray(buf, len), expectedString);
         QCOMPARE(int(stream.status()), expectedStatus);
         delete [] buf;