diff --git a/src/corelib/plugin/quuid.h b/src/corelib/plugin/quuid.h
index b8bb5bd95ac..299ce76d7b4 100644
--- a/src/corelib/plugin/quuid.h
+++ b/src/corelib/plugin/quuid.h
@@ -246,26 +246,40 @@ inline QUuid QUuid::fromBytes(const void *bytes, QSysInfo::Endian order) noexcep
 constexpr QUuid::QUuid(quint128 uuid, QSysInfo::Endian order) noexcept
     : QUuid()
 {
-    if (order == QSysInfo::LittleEndian)
-        uuid = qbswap(uuid);
-    data1 = uint(uuid >> 96);
-    data2 = ushort(uuid >> 80);
-    data3 = ushort(uuid >> 64);
-    for (int i = 0; i < 8; ++i)
-        data4[i] = uchar(uuid >> (56 - i * 8));
+    if (order == QSysInfo::BigEndian) {
+        data1 = qFromBigEndian<quint32>(int(uuid));
+        data2 = qFromBigEndian<quint16>(ushort(uuid >> 32));
+        data3 = qFromBigEndian<quint16>(ushort(uuid >> 48));
+        for (int i = 0; i < 8; ++i)
+            data4[i] = uchar(uuid >> (64 + i * 8));
+    } else {
+        data1 = qFromLittleEndian<quint32>(uint(uuid >> 96));
+        data2 = qFromLittleEndian<quint16>(ushort(uuid >> 80));
+        data3 = qFromLittleEndian<quint16>(ushort(uuid >> 64));
+        for (int i = 0; i < 8; ++i)
+            data4[i] = uchar(uuid >> (56 - i * 8));
+    }
 }
 
 constexpr quint128 QUuid::toUInt128(QSysInfo::Endian order) const noexcept
 {
     quint128 result = {};
-    result = data1;
-    result <<= 32;
-    result |= (data2 << 16) | uint(data3);
-    result <<= 64;
-    for (int i = 0; i < 8; ++i)
-        result |= quint64(data4[i]) << (56 - i * 8);
-    if (order == QSysInfo::LittleEndian)
-        return qbswap(result);
+    if (order == QSysInfo::BigEndian) {
+        for (int i = 0; i < 8; ++i)
+            result |= quint64(data4[i]) << (i * 8);
+        result = result << 64;
+        result |= quint64(qToBigEndian<quint16>(data3)) << 48;
+        result |= quint64(qToBigEndian<quint16>(data2)) << 32;
+        result |= qToBigEndian<quint32>(data1);
+    } else {
+        result = qToLittleEndian<quint32>(data1);
+        result = result << 32;
+        result |= quint64(qToLittleEndian<quint16>(data2)) << 16;
+        result |= quint64(qToLittleEndian<quint16>(data3));
+        result = result << 64;
+        for (int i = 0; i < 8; ++i)
+            result |= quint64(data4[i]) << (56 - i * 8);
+    }
     return result;
 }
 #endif
diff --git a/tests/auto/corelib/plugin/quuid/tst_quuid.cpp b/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
index e759bdac856..b9fcf585fb1 100644
--- a/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
+++ b/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
@@ -250,15 +250,16 @@ void tst_QUuid::uint128()
 {
 #ifdef __SIZEOF_INT128__
     constexpr quint128 u = quint128(Q_UINT64_C(0xfc69b59ecc344436)) << 64
-                            | Q_UINT64_C(0xa43cee95d128b8c5);
-    constexpr QUuid uuid(u);
-    static_assert(uuid.toUInt128() == u, "Round-trip through QUuid failed");
+                            | Q_UINT64_C(0xa43cee95d128b8c5); // This is LE
+    constexpr quint128 be = qToBigEndian(u);
+    constexpr QUuid uuid(be);
+    static_assert(uuid.toUInt128() == be, "Round-trip through QUuid failed");
 
     QCOMPARE(uuid, uuidA);
-    QCOMPARE(quint64(uuid.toUInt128() >> 64), quint64(u >> 64));
-    QCOMPARE(quint64(uuid.toUInt128()), quint64(u));
+    QCOMPARE(quint64(uuid.toUInt128() >> 64), quint64(be >> 64));
+    QCOMPARE(quint64(uuid.toUInt128()), quint64(be));
 
-    quint128 le = qFromBigEndian(u);
+    quint128 le = qFromBigEndian(be);
     QCOMPARE(quint64(uuid.toUInt128(QSysInfo::LittleEndian) >> 64), quint64(le >> 64));
     QCOMPARE(quint64(uuid.toUInt128(QSysInfo::LittleEndian)), quint64(le));
     QCOMPARE(QUuid(le, QSysInfo::LittleEndian), uuidA);
@@ -266,6 +267,11 @@ void tst_QUuid::uint128()
     QUuid::Id128Bytes bytes = { .data128 = { qToBigEndian(u) } };
     QUuid uuid2(bytes);
     QCOMPARE(uuid2, uuid);
+
+    // verify that toBytes() and toUInt128() provide bytewise similar result
+    constexpr quint128 val = uuid.toUInt128();
+    bytes = uuid.toBytes();
+    QVERIFY(memcmp(&val, bytes.data, sizeof(val)) == 0);
 #else
     QSKIP("This platform has no support for 128-bit integer");
 #endif