diff --git a/src/corelib/compat/removed_api.cpp b/src/corelib/compat/removed_api.cpp
index 827bed9bf74..df30d44aa8c 100644
--- a/src/corelib/compat/removed_api.cpp
+++ b/src/corelib/compat/removed_api.cpp
@@ -1240,6 +1240,22 @@ QUuid QUuid::createUuidV5(const QUuid &ns, const QByteArray &baseData) noexcept
 
 #if QT_CORE_REMOVED_SINCE(6, 9)
 
+#include "quuid.h"
+
+bool QUuid::isNull() const noexcept
+{
+    return isNull(QT6_CALL_NEW_OVERLOAD);
+}
+
+QUuid::Variant QUuid::variant() const noexcept
+{
+    return variant(QT6_CALL_NEW_OVERLOAD);
+}
+
+QUuid::Version QUuid::version() const noexcept
+{
+    return version(QT6_CALL_NEW_OVERLOAD);
+}
 
 // #include "qotherheader.h"
 // // implement removed functions from qotherheader.h
diff --git a/src/corelib/plugin/quuid.cpp b/src/corelib/plugin/quuid.cpp
index af7c07d23e6..3dcfa1faf2c 100644
--- a/src/corelib/plugin/quuid.cpp
+++ b/src/corelib/plugin/quuid.cpp
@@ -823,15 +823,11 @@ QDataStream &operator>>(QDataStream &s, QUuid &id)
 #endif // QT_NO_DATASTREAM
 
 /*!
+    \fn bool QUuid::isNull() const
+
     Returns \c true if this is the null UUID
     {00000000-0000-0000-0000-000000000000}; otherwise returns \c false.
 */
-bool QUuid::isNull() const noexcept
-{
-    return data4[0] == 0 && data4[1] == 0 && data4[2] == 0 && data4[3] == 0 &&
-           data4[4] == 0 && data4[5] == 0 && data4[6] == 0 && data4[7] == 0 &&
-           data1 == 0 && data2 == 0 && data3 == 0;
-}
 
 /*!
     \enum QUuid::Variant
@@ -875,17 +871,6 @@ bool QUuid::isNull() const noexcept
 
     \sa version()
 */
-QUuid::Variant QUuid::variant() const noexcept
-{
-    if (isNull())
-        return VarUnknown;
-    // Check the 3 MSB of data4[0]
-    if ((data4[0] & 0x80) == 0x00) return NCS;
-    else if ((data4[0] & 0xC0) == 0x80) return DCE;
-    else if ((data4[0] & 0xE0) == 0xC0) return Microsoft;
-    else if ((data4[0] & 0xE0) == 0xE0) return Reserved;
-    return VarUnknown;
-}
 
 /*!
     \fn QUuid::Version QUuid::version() const
@@ -896,17 +881,6 @@ QUuid::Variant QUuid::variant() const noexcept
 
     \sa variant()
 */
-QUuid::Version QUuid::version() const noexcept
-{
-    // Check the 4 MSB of data3
-    Version ver = (Version)(data3>>12);
-    if (isNull()
-         || (variant() != DCE)
-         || ver < Time
-         || ver > Sha1)
-        return VerUnknown;
-    return ver;
-}
 
 /*!
     \fn bool QUuid::operator<(const QUuid &lhs, const QUuid &rhs)
diff --git a/src/corelib/plugin/quuid.h b/src/corelib/plugin/quuid.h
index 435b7bb572d..c6aea2591c8 100644
--- a/src/corelib/plugin/quuid.h
+++ b/src/corelib/plugin/quuid.h
@@ -117,7 +117,25 @@ QT_WARNING_POP
 #endif
     static QUuid fromRfc4122(QByteArrayView) noexcept;
 
+#if QT_CORE_REMOVED_SINCE(6, 9)
     bool isNull() const noexcept;
+#endif
+    constexpr bool isNull(QT6_DECL_NEW_OVERLOAD) const noexcept
+    {
+#if defined(__cpp_lib_bit_cast) && defined(QT_SUPPORTS_INT128)
+        return std::bit_cast<quint128>(*this) == 0;
+#else
+        // QNX fails to compile
+        // data4[0] == 0 && data4[1] == 0 && ...
+        // in constexpr context, so rewrite it using a loop. This way we have
+        // only single data4[i] != 0 check at each iteration
+        for (size_t i = 0; i < 8; ++i) {
+            if (data4[i] != 0)
+                return false;
+        }
+        return data1 == 0 && data2 == 0 && data3 == 0;
+#endif
+    }
 
 #ifdef QT_SUPPORTS_INT128
     static constexpr QUuid fromUInt128(quint128 uuid, QSysInfo::Endian order = QSysInfo::BigEndian) noexcept;
@@ -253,8 +271,29 @@ public:
         return QUuid::createUuidV5(ns, qToByteArrayViewIgnoringNull(baseData.toUtf8()));
     }
 
+#if QT_CORE_REMOVED_SINCE(6, 9)
     QUuid::Variant variant() const noexcept;
     QUuid::Version version() const noexcept;
+#endif
+    constexpr Variant variant(QT6_DECL_NEW_OVERLOAD) const noexcept
+    {
+        // Check the 3 MSB of data4[0]
+        const quint8 var = data4[0] & 0xE0;
+        if (var < 0x80)
+            return isNull(QT6_CALL_NEW_OVERLOAD) ? VarUnknown : NCS;
+        if (var < 0xC0)
+            return DCE;
+        return Variant(var >> 5); // Microsoft or Reserved
+    }
+    constexpr Version version(QT6_DECL_NEW_OVERLOAD) const noexcept
+    {
+        // Check the 4 MSB of data3
+        const Version ver = Version(data3 >> 12);
+        // Check that variant() == DCE and version is in a valid range
+        if (ver >= Time && ver <= Sha1 && (data4[0] & 0xC0) == 0x80)
+            return ver;
+        return VerUnknown;
+    }
 
 #if defined(Q_OS_DARWIN) || defined(Q_QDOC)
     static QUuid fromCFUUID(CFUUIDRef uuid);
diff --git a/tests/auto/corelib/plugin/quuid/tst_quuid.cpp b/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
index d2a7cdf7c36..3527764f931 100644
--- a/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
+++ b/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
@@ -349,6 +349,12 @@ void tst_QUuid::check_QDataStream()
 
 void tst_QUuid::isNull()
 {
+    constexpr QUuid null;
+    static_assert(null.isNull());
+
+    constexpr QUuid nonNull{1, 2, 3, 4, 0, 1, 2, 3, 4, 5, 6};
+    static_assert(!nonNull.isNull());
+
     QVERIFY( !uuidA.isNull() );
 
     QUuid should_be_null_uuid;
@@ -561,6 +567,12 @@ void tst_QUuid::variants_data()
     QTest::newRow("uuidA") << uuidA << QUuid::DCE;
     QTest::newRow("uuidB") << uuidB << QUuid::DCE;
     QTest::newRow("NCS") << QUuid("{3a2f883c-4000-000d-0000-00fb40000000}") << QUuid::NCS;
+
+    // compile-time checks
+    constexpr QUuid defaultConstructed;
+    static_assert(defaultConstructed.variant() == QUuid::Variant::VarUnknown);
+    constexpr QUuid minDCE = make_minimal(QUuid::Variant::DCE);
+    static_assert(minDCE.variant() == QUuid::Variant::DCE);
 }
 
 void tst_QUuid::variants()
@@ -607,6 +619,12 @@ void tst_QUuid::versions_data()
             << QUuid::VerUnknown;
     QTest::newRow("uuidA") << uuidA << QUuid::Random;
     QTest::newRow("uuidB") << uuidB << QUuid::Random;
+
+    // compile-time checks
+    constexpr QUuid defaultConstructed;
+    static_assert(defaultConstructed.version() == QUuid::Version::VerUnknown);
+    constexpr QUuid timeVer = {0, 0, 0x1000, 0b1000'0000, 0, 0, 0, 0, 0, 0, 0};
+    static_assert(timeVer.version() == QUuid::Version::Time);
 }
 
 void tst_QUuid::versions()