diff --git a/src/corelib/serialization/qjsonobject.cpp b/src/corelib/serialization/qjsonobject.cpp
index 99f5507aa12..3e0857dc954 100644
--- a/src/corelib/serialization/qjsonobject.cpp
+++ b/src/corelib/serialization/qjsonobject.cpp
@@ -1445,7 +1445,7 @@ void QJsonObject::removeAt(qsizetype index)
 
 size_t qHash(const QJsonObject &object, size_t seed)
 {
-    QtPrivate::QHashCombine hash;
+    QtPrivate::QHashCombine hash(seed);
     for (auto it = object.begin(), end = object.end(); it != end; ++it) {
         const QString key = it.key();
         const QJsonValue value = it.value();
diff --git a/src/corelib/tools/qhash.h b/src/corelib/tools/qhash.h
index 24c014e2153..87713b93a77 100644
--- a/src/corelib/tools/qhash.h
+++ b/src/corelib/tools/qhash.h
@@ -2710,9 +2710,9 @@ template <class Key, class T>
 size_t qHash(const QHash<Key, T> &key, size_t seed = 0)
     noexcept(noexcept(qHash(std::declval<Key&>())) && noexcept(qHash(std::declval<T&>())))
 {
+    const QtPrivate::QHashCombine combine(seed);
     size_t hash = 0;
     for (auto it = key.begin(), end = key.end(); it != end; ++it) {
-        QtPrivate::QHashCombine combine;
         size_t h = combine(seed, it.key());
         // use + to keep the result independent of the ordering of the keys
         hash += combine(h, it.value());
@@ -2724,9 +2724,9 @@ template <class Key, class T>
 inline size_t qHash(const QMultiHash<Key, T> &key, size_t seed = 0)
     noexcept(noexcept(qHash(std::declval<Key&>())) && noexcept(qHash(std::declval<T&>())))
 {
+    const QtPrivate::QHashCombine combine(seed);
     size_t hash = 0;
     for (auto it = key.begin(), end = key.end(); it != end; ++it) {
-        QtPrivate::QHashCombine combine;
         size_t h = combine(seed, it.key());
         // use + to keep the result independent of the ordering of the keys
         hash += combine(h, it.value());
diff --git a/src/corelib/tools/qhashfunctions.h b/src/corelib/tools/qhashfunctions.h
index c687cdaeb72..cbe217db11e 100644
--- a/src/corelib/tools/qhashfunctions.h
+++ b/src/corelib/tools/qhashfunctions.h
@@ -298,18 +298,40 @@ bool qHashEquals(const T1 &a, const T2 &b)
 }
 
 namespace QtPrivate {
-
-struct QHashCombine
+template <typename Mixer> struct QHashCombiner : private Mixer
 {
-    typedef size_t result_type;
+    using result_type = typename Mixer::result_type ;
+
+#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0) || defined(QT_BOOTSTRAPPED)
+    // Qt 6.x didn't use to pass the seed; bootstrap has no seed
+    static constexpr size_t seed = 0;
+    constexpr QHashCombiner(result_type) noexcept {}
+    Q_DECL_DEPRECATED_X("pass the seed argument") constexpr QHashCombiner() noexcept {}
+#else
+    size_t seed;
+    constexpr QHashCombiner(result_type s) : seed(s) noexcept {}
+#endif
+
     template <typename T>
-    constexpr result_type operator()(size_t seed, const T &t) const
+    constexpr result_type operator()(result_type result, const T &t) const
         noexcept(noexcept(qHash(t, seed)))
-    // combiner taken from N3876 / boost::hash_combine
-    { return seed ^ (qHash(t, size_t(0)) + 0x9e3779b9 + (seed << 6) + (seed >> 2)); }
+    {
+        return Mixer::operator()(result, qHash(t, seed));
+    }
 };
 
-struct QHashCombineCommutative
+struct QHashCombineMixer
+{
+    typedef size_t result_type;
+    constexpr result_type operator()(result_type result, result_type hash) const noexcept
+    {
+        // combiner taken from N3876 / boost::hash_combine
+        return result ^ (hash + 0x9e3779b9 + (result << 6) + (result >> 2));
+    }
+};
+using QHashCombine = QHashCombiner<QHashCombineMixer>;
+
+struct QHashCombineCommutativeMixer : std::plus<size_t>
 {
     // QHashCombine is a good hash combiner, but is not commutative,
     // ie. it depends on the order of the input elements. That is
@@ -317,11 +339,8 @@ struct QHashCombineCommutative
     // {1,3,0}. Except when it isn't (e.g. for QSet and
     // QHash). Therefore, provide a commutative combiner, too.
     typedef size_t result_type;
-    template <typename T>
-    constexpr result_type operator()(size_t seed, const T &t) const
-        noexcept(noexcept(qHash(t, seed)))
-    { return seed + qHash(t, size_t(0)); } // don't use xor!
 };
+using QHashCombineCommutative = QHashCombiner<QHashCombineCommutativeMixer>;
 
 template <typename... T>
 using QHashMultiReturnType = decltype(
@@ -356,7 +375,7 @@ QtPrivate::QHashMultiReturnType<T...>
 qHashMulti(size_t seed, const T &... args)
     noexcept(std::conjunction_v<QtPrivate::QNothrowHashable<T>...>)
 {
-    QtPrivate::QHashCombine hash;
+    QtPrivate::QHashCombine hash(seed);
     return ((seed = hash(seed, args)), ...), seed;
 }
 
@@ -370,7 +389,7 @@ QtPrivate::QHashMultiReturnType<T...>
 qHashMultiCommutative(size_t seed, const T &... args)
     noexcept(std::conjunction_v<QtPrivate::QNothrowHashable<T>...>)
 {
-    QtPrivate::QHashCombineCommutative hash;
+    QtPrivate::QHashCombineCommutative hash(seed);
     return ((seed = hash(seed, args)), ...), seed;
 }
 
@@ -378,14 +397,14 @@ template <typename InputIterator>
 inline size_t qHashRange(InputIterator first, InputIterator last, size_t seed = 0)
     noexcept(noexcept(qHash(*first))) // assume iterator operations don't throw
 {
-    return std::accumulate(first, last, seed, QtPrivate::QHashCombine());
+    return std::accumulate(first, last, seed, QtPrivate::QHashCombine(seed));
 }
 
 template <typename InputIterator>
 inline size_t qHashRangeCommutative(InputIterator first, InputIterator last, size_t seed = 0)
     noexcept(noexcept(qHash(*first))) // assume iterator operations don't throw
 {
-    return std::accumulate(first, last, seed, QtPrivate::QHashCombineCommutative());
+    return std::accumulate(first, last, seed, QtPrivate::QHashCombineCommutative(seed));
 }
 
 namespace QHashPrivate {
diff --git a/src/corelib/tools/qmap.h b/src/corelib/tools/qmap.h
index 01e614aa28b..ac2f04b8cd8 100644
--- a/src/corelib/tools/qmap.h
+++ b/src/corelib/tools/qmap.h
@@ -810,7 +810,7 @@ private:
             return seed;
         // don't use qHashRange to avoid its compile-time overhead:
         return std::accumulate(key.d->m.begin(), key.d->m.end(), seed,
-                               QtPrivate::QHashCombine{});
+                               QtPrivate::QHashCombine{seed});
     }
 #endif // !Q_QDOC
 };
diff --git a/src/gui/painting/qtransform.cpp b/src/gui/painting/qtransform.cpp
index 1ea63f40965..66f1cf2a985 100644
--- a/src/gui/painting/qtransform.cpp
+++ b/src/gui/painting/qtransform.cpp
@@ -784,7 +784,7 @@ bool QTransform::operator==(const QTransform &o) const
 */
 size_t qHash(const QTransform &key, size_t seed) noexcept
 {
-    QtPrivate::QHashCombine hash;
+    QtPrivate::QHashCombine hash(seed);
     seed = hash(seed, key.m11());
     seed = hash(seed, key.m12());
     seed = hash(seed, key.m21());
diff --git a/src/gui/rhi/qrhi.cpp b/src/gui/rhi/qrhi.cpp
index 42e7753e4cb..0628d07ce73 100644
--- a/src/gui/rhi/qrhi.cpp
+++ b/src/gui/rhi/qrhi.cpp
@@ -6543,7 +6543,7 @@ bool operator!=(const QRhiShaderResourceBinding &a, const QRhiShaderResourceBind
 size_t qHash(const QRhiShaderResourceBinding &b, size_t seed) noexcept
 {
     const QRhiShaderResourceBinding::Data *d = QRhiImplementation::shaderResourceBindingData(b);
-    QtPrivate::QHashCombine hash;
+    QtPrivate::QHashCombine hash(seed);
     seed = hash(seed, d->binding);
     seed = hash(seed, d->stage);
     seed = hash(seed, d->type);
diff --git a/src/gui/rhi/qrhi.h b/src/gui/rhi/qrhi.h
index 5776554916a..66651dcf979 100644
--- a/src/gui/rhi/qrhi.h
+++ b/src/gui/rhi/qrhi.h
@@ -69,7 +69,7 @@ private:
 
     friend size_t qHash(const QRhiDepthStencilClearValue &v, size_t seed = 0) noexcept
     {
-        QtPrivate::QHashCombine hash;
+        QtPrivate::QHashCombine hash(seed);
         seed = hash(seed, v.m_d);
         seed = hash(seed, v.m_s);
         return seed;
@@ -118,7 +118,7 @@ private:
 
     friend size_t qHash(const QRhiViewport &v, size_t seed = 0) noexcept
     {
-        QtPrivate::QHashCombine hash;
+        QtPrivate::QHashCombine hash(seed);
         seed = hash(seed, v.m_rect[0]);
         seed = hash(seed, v.m_rect[1]);
         seed = hash(seed, v.m_rect[2]);
@@ -161,7 +161,7 @@ private:
 
     friend size_t qHash(const QRhiScissor &v, size_t seed = 0) noexcept
     {
-        QtPrivate::QHashCombine hash;
+        QtPrivate::QHashCombine hash(seed);
         seed = hash(seed, v.m_rect[0]);
         seed = hash(seed, v.m_rect[1]);
         seed = hash(seed, v.m_rect[2]);
@@ -215,7 +215,7 @@ private:
 
     friend size_t qHash(const QRhiVertexInputBinding &v, size_t seed = 0) noexcept
     {
-        QtPrivate::QHashCombine hash;
+        QtPrivate::QHashCombine hash(seed);
         seed = hash(seed, v.m_stride);
         seed = hash(seed, v.m_classification);
         seed = hash(seed, v.m_instanceStepRate);
@@ -303,7 +303,7 @@ private:
 
     friend size_t qHash(const QRhiVertexInputAttribute &v, size_t seed = 0) noexcept
     {
-        QtPrivate::QHashCombine hash;
+        QtPrivate::QHashCombine hash(seed);
         seed = hash(seed, v.m_binding);
         seed = hash(seed, v.m_location);
         seed = hash(seed, v.m_format);
@@ -363,7 +363,7 @@ private:
 
     friend size_t qHash(const QRhiVertexInputLayout &v, size_t seed = 0) noexcept
     {
-        QtPrivate::QHashCombine hash;
+        QtPrivate::QHashCombine hash(seed);
         seed = hash(seed, v.m_bindings);
         seed = hash(seed, v.m_attributes);
         return seed;
@@ -420,7 +420,7 @@ private:
 
     friend size_t qHash(const QRhiShaderStage &v, size_t seed = 0) noexcept
     {
-        QtPrivate::QHashCombine hash;
+        QtPrivate::QHashCombine hash(seed);
         seed = hash(seed, v.m_type);
         seed = hash(seed, v.m_shader);
         seed = hash(seed, v.m_shaderVariant);
diff --git a/src/gui/rhi/qrhid3d12_p.h b/src/gui/rhi/qrhid3d12_p.h
index 2381bb40d42..caa428c6cbc 100644
--- a/src/gui/rhi/qrhid3d12_p.h
+++ b/src/gui/rhi/qrhid3d12_p.h
@@ -507,7 +507,7 @@ struct Q_D3D12_SAMPLER_DESC
 
     friend size_t qHash(const Q_D3D12_SAMPLER_DESC &key, size_t seed = 0) noexcept
     {
-        QtPrivate::QHashCombine hash;
+        QtPrivate::QHashCombine hash(seed);
         seed = hash(seed, key.desc.Filter);
         seed = hash(seed, key.desc.AddressU);
         seed = hash(seed, key.desc.AddressV);
diff --git a/src/gui/rhi/qshader.cpp b/src/gui/rhi/qshader.cpp
index e1fe23c2a2f..5e967c62e40 100644
--- a/src/gui/rhi/qshader.cpp
+++ b/src/gui/rhi/qshader.cpp
@@ -812,7 +812,7 @@ bool operator==(const QShader &lhs, const QShader &rhs) noexcept
 size_t qHash(const QShader &s, size_t seed) noexcept
 {
     if (s.d) {
-        QtPrivate::QHashCombine hash;
+        QtPrivate::QHashCombine hash(seed);
         seed = hash(seed, s.stage());
         if (!s.d->shaders.isEmpty()) {
             seed = hash(seed, s.d->shaders.firstKey());
diff --git a/src/gui/text/qfontdatabase_p.h b/src/gui/text/qfontdatabase_p.h
index 58feb9457b9..cbfa02b2b7c 100644
--- a/src/gui/text/qfontdatabase_p.h
+++ b/src/gui/text/qfontdatabase_p.h
@@ -51,7 +51,7 @@ inline bool operator!=(const QtFontFallbacksCacheKey &lhs, const QtFontFallbacks
 
 inline size_t qHash(const QtFontFallbacksCacheKey &key, size_t seed = 0) noexcept
 {
-    QtPrivate::QHashCombine hash;
+    QtPrivate::QHashCombine hash(seed);
     seed = hash(seed, key.family);
     seed = hash(seed, int(key.style));
     seed = hash(seed, int(key.styleHint));
diff --git a/src/gui/vulkan/qvulkaninstance.h b/src/gui/vulkan/qvulkaninstance.h
index 819751025be..2728fc2e1b0 100644
--- a/src/gui/vulkan/qvulkaninstance.h
+++ b/src/gui/vulkan/qvulkaninstance.h
@@ -81,7 +81,7 @@ inline bool operator!=(const QVulkanLayer &lhs, const QVulkanLayer &rhs) noexcep
 
 inline size_t qHash(const QVulkanLayer &key, size_t seed = 0) noexcept
 {
-    QtPrivate::QHashCombine hash;
+    QtPrivate::QHashCombine hash(seed);
     seed = hash(seed, key.name);
     seed = hash(seed, key.version);
     seed = hash(seed, key.specVersion);
@@ -104,7 +104,7 @@ inline bool operator!=(const QVulkanExtension &lhs, const QVulkanExtension &rhs)
 
 inline size_t qHash(const QVulkanExtension &key, size_t seed = 0) noexcept
 {
-    QtPrivate::QHashCombine hash;
+    QtPrivate::QHashCombine hash(seed);
     seed = hash(seed, key.name);
     seed = hash(seed, key.version);
     return seed;