diff --git a/src/corelib/kernel/qmetatype.cpp b/src/corelib/kernel/qmetatype.cpp
index 130b30481d..780ae10396 100644
--- a/src/corelib/kernel/qmetatype.cpp
+++ b/src/corelib/kernel/qmetatype.cpp
@@ -75,8 +75,11 @@ struct QMetaTypeCustomRegistry
     // index of first empty (unregistered) type in registry, if any.
     int firstEmpty = 0;
 
-    int registerCustomType(const QtPrivate::QMetaTypeInterface *ti)
+    int registerCustomType(const QtPrivate::QMetaTypeInterface *cti)
     {
+        // we got here because cti->typeId is 0, so this is a custom meta type
+        // (not read-only)
+        auto ti = const_cast<QtPrivate::QMetaTypeInterface *>(cti);
         {
             QWriteLocker l(&lock);
             if (int id = ti->typeId.loadRelaxed())
@@ -789,9 +792,11 @@ bool QMetaType::isOrdered() const
 void QMetaType::unregisterMetaType(QMetaType type)
 {
     if (type.d_ptr && type.d_ptr->typeId.loadRelaxed() >= QMetaType::User) {
+        // this is a custom meta type (not read-only)
+        auto d = const_cast<QtPrivate::QMetaTypeInterface *>(type.d_ptr);
         if (auto reg = customTypeRegistry())
-            reg->unregisterDynamicType(type.d_ptr->typeId.loadRelaxed());
-        type.d_ptr->typeId.storeRelease(0);
+            reg->unregisterDynamicType(d->typeId.loadRelaxed());
+        d->typeId.storeRelease(0);
     }
 }
 
diff --git a/src/corelib/kernel/qmetatype.h b/src/corelib/kernel/qmetatype.h
index a2639c1dfa..82d799ac41 100644
--- a/src/corelib/kernel/qmetatype.h
+++ b/src/corelib/kernel/qmetatype.h
@@ -225,6 +225,20 @@ struct QMetaObject;
 namespace QtPrivate
 {
 
+class QMetaTypeInterface;
+
+// MSVC is the only supported compiler that includes the type of a variable in
+// its mangled form, so it's not binary-compatible to drop the const in
+// QMetaTypeInterfaceWrapper::metaType for it, which means we must keep the
+// mutable field until Qt 7.
+#if QT_VERSION >= QT_VERSION_CHECK(7, 0, 0) || defined(QT_BOOTSTRAPPED) || !defined(Q_CC_MSVC)
+#  define QMTI_MUTABLE
+using NonConstMetaTypeInterface = QMetaTypeInterface;
+#else
+#  define QMTI_MUTABLE mutable
+using NonConstMetaTypeInterface = const QMetaTypeInterface;
+#endif
+
 class QMetaTypeInterface
 {
 public:
@@ -232,7 +246,7 @@ public:
     ushort alignment;
     uint size;
     uint flags;
-    mutable QBasicAtomicInt typeId;
+    QMTI_MUTABLE QBasicAtomicInt typeId;
 
     using MetaObjectFn = const QMetaObject *(*)(const QMetaTypeInterface *);
     MetaObjectFn metaObjectFn;
@@ -261,6 +275,7 @@ public:
     using LegacyRegisterOp = void (*)();
     LegacyRegisterOp legacyRegisterOp;
 };
+#undef QMTI_MUTABLE
 
 /*!
     This template is used for implicit conversion from type From to type To.
@@ -2326,7 +2341,13 @@ public:
 template<typename T>
 struct QMetaTypeInterfaceWrapper
 {
-    static inline constexpr const QMetaTypeInterface metaType = {
+    // if the type ID for T is known at compile-time, then we can declare
+    // the QMetaTypeInterface object const; otherwise, we declare it as
+    // non-const and the .typeId is updated by QMetaType::idHelper().
+    static constexpr bool IsConstMetaTypeInterface = !!BuiltinMetaType<T>::value;
+    using InterfaceType = std::conditional_t<IsConstMetaTypeInterface, const QMetaTypeInterface, NonConstMetaTypeInterface>;
+
+    static inline InterfaceType metaType = {
         /*.revision=*/ 0,
         /*.alignment=*/ alignof(T),
         /*.size=*/ sizeof(T),