diff --git a/src/corelib/global/qendian.h b/src/corelib/global/qendian.h
index 9cd0044cbc6..29d632ef04d 100644
--- a/src/corelib/global/qendian.h
+++ b/src/corelib/global/qendian.h
@@ -105,6 +105,23 @@ inline constexpr T qbswap(T source)
     return T(qbswap_helper(typename QIntegerForSizeof<T>::Unsigned(source)));
 }
 
+#ifdef __SIZEOF_INT128__
+// extra definitions for q(u)int128, in case std::is_integral_v<~~> == false
+inline constexpr quint128 qbswap(quint128 source)
+{
+    quint128 result = {};
+    result = qbswap_helper(quint64(source));
+    result <<= 64;
+    result |= qbswap_helper(quint64(source >> 64));
+    return result;
+}
+
+inline constexpr quint128 qbswap(qint128 source)
+{
+    return qint128(qbswap(quint128(source)));
+}
+#endif
+
 // floating specializations
 template<typename Float>
 Float qbswapFloatHelper(Float source)
diff --git a/src/corelib/global/qtypes.h b/src/corelib/global/qtypes.h
index d08a919c136..412ab3af623 100644
--- a/src/corelib/global/qtypes.h
+++ b/src/corelib/global/qtypes.h
@@ -58,6 +58,11 @@ typedef unsigned long long quint64; /* 64 bit unsigned */
 typedef qint64 qlonglong;
 typedef quint64 qulonglong;
 
+#if defined(__SIZEOF_INT128__)
+__extension__ typedef __int128_t qint128;
+__extension__ typedef __uint128_t quint128;
+#endif
+
 #ifndef __cplusplus
 // In C++ mode, we define below using QIntegerForSize template
 static_assert(sizeof(ptrdiff_t) == sizeof(size_t), "Weird ptrdiff_t and size_t definitions");
@@ -103,7 +108,7 @@ template <>    struct QIntegerForSize<2> { typedef quint16 Unsigned; typedef qin
 template <>    struct QIntegerForSize<4> { typedef quint32 Unsigned; typedef qint32 Signed; };
 template <>    struct QIntegerForSize<8> { typedef quint64 Unsigned; typedef qint64 Signed; };
 #if defined(Q_CC_GNU) && defined(__SIZEOF_INT128__)
-template <>    struct QIntegerForSize<16> { __extension__ typedef unsigned __int128 Unsigned; __extension__ typedef __int128 Signed; };
+template <>    struct QIntegerForSize<16> { typedef quint128 Unsigned; typedef qint128 Signed; };
 #endif
 template <class T> struct QIntegerForSizeof: QIntegerForSize<sizeof(T)> { };
 typedef QIntegerForSize<Q_PROCESSOR_WORDSIZE>::Signed qregisterint;