diff --git a/src/corelib/global/qendian.h b/src/corelib/global/qendian.h
index 29d632ef04..60c4a7b174 100644
--- a/src/corelib/global/qendian.h
+++ b/src/corelib/global/qendian.h
@@ -105,7 +105,7 @@ inline constexpr T qbswap(T source)
     return T(qbswap_helper(typename QIntegerForSizeof<T>::Unsigned(source)));
 }
 
-#ifdef __SIZEOF_INT128__
+#ifdef QT_SUPPORTS_INT128
 // extra definitions for q(u)int128, in case std::is_integral_v<~~> == false
 inline constexpr quint128 qbswap(quint128 source)
 {
diff --git a/src/corelib/global/qtypes.h b/src/corelib/global/qtypes.h
index 954f22a191..6a4b6acf39 100644
--- a/src/corelib/global/qtypes.h
+++ b/src/corelib/global/qtypes.h
@@ -58,7 +58,13 @@ typedef unsigned long long quint64; /* 64 bit unsigned */
 typedef qint64 qlonglong;
 typedef quint64 qulonglong;
 
-#if defined(__SIZEOF_INT128__)
+#if defined(__SIZEOF_INT128__) && !defined(QT_NO_INT128)
+#  define QT_SUPPORTS_INT128 __SIZEOF_INT128__
+#else
+#  undef QT_SUPPORTS_INT128
+#endif
+
+#if defined(QT_SUPPORTS_INT128)
 __extension__ typedef __int128_t qint128;
 __extension__ typedef __uint128_t quint128;
 #endif
@@ -107,7 +113,7 @@ template <>    struct QIntegerForSize<1> { typedef quint8  Unsigned; typedef qin
 template <>    struct QIntegerForSize<2> { typedef quint16 Unsigned; typedef qint16 Signed; };
 template <>    struct QIntegerForSize<4> { typedef quint32 Unsigned; typedef qint32 Signed; };
 template <>    struct QIntegerForSize<8> { typedef quint64 Unsigned; typedef qint64 Signed; };
-#if defined(__SIZEOF_INT128__)
+#if defined(QT_SUPPORTS_INT128)
 template <>    struct QIntegerForSize<16> { typedef quint128 Unsigned; typedef qint128 Signed; };
 #endif
 template <class T> struct QIntegerForSizeof: QIntegerForSize<sizeof(T)> { };
diff --git a/src/corelib/plugin/quuid.h b/src/corelib/plugin/quuid.h
index ddd24eb678..2cefb4d764 100644
--- a/src/corelib/plugin/quuid.h
+++ b/src/corelib/plugin/quuid.h
@@ -60,7 +60,7 @@ public:
         quint16 data16[8];
         quint32 data32[4];
         quint64 data64[2];
-#ifdef __SIZEOF_INT128__
+#ifdef QT_SUPPORTS_INT128
         quint128 data128[1];
 #endif
 
@@ -100,7 +100,7 @@ public:
 
     bool isNull() const noexcept;
 
-#ifdef __SIZEOF_INT128__
+#ifdef QT_SUPPORTS_INT128
     constexpr QUuid(quint128 uuid, QSysInfo::Endian order = QSysInfo::BigEndian) noexcept;
     constexpr quint128 toUInt128(QSysInfo::Endian order = QSysInfo::BigEndian) const noexcept;
 #endif
@@ -242,7 +242,7 @@ inline QUuid QUuid::fromBytes(const void *bytes, QSysInfo::Endian order) noexcep
     return QUuid(result, order);
 }
 
-#ifdef __SIZEOF_INT128__
+#ifdef QT_SUPPORTS_INT128
 constexpr QUuid::QUuid(quint128 uuid, QSysInfo::Endian order) noexcept
     : QUuid()
 {
diff --git a/tests/auto/corelib/plugin/quuid/tst_quuid.cpp b/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
index b9fcf585fb..08f548a834 100644
--- a/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
+++ b/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
@@ -248,7 +248,7 @@ void tst_QUuid::id128()
 
 void tst_QUuid::uint128()
 {
-#ifdef __SIZEOF_INT128__
+#ifdef QT_SUPPORTS_INT128
     constexpr quint128 u = quint128(Q_UINT64_C(0xfc69b59ecc344436)) << 64
                             | Q_UINT64_C(0xa43cee95d128b8c5); // This is LE
     constexpr quint128 be = qToBigEndian(u);