Cannot declare MetaType for a QHash/QMultiHash with key type without custom operator==

struct Empty {};
struct NoCmpKeyHash : public QHash<Empty, int>
{
    // Works if this is uncommented
    // bool operator==(const NoCmpKeyHash &) const = delete;
};
uint qHash(const Empty &) { return 0; }

Q_DECLARE_METATYPE(NoCmpKeyHash);

../../cmake-build/qtbase/include/QtCore/../../../../qt5/qtbase/src/corelib/tools/qhashfunctions.h: In instantiation of ‘bool qHashEquals(const T&, const T&) [with T = Empty]’:
../../cmake-build/qtbase/include/QtCore/../../../../qt5/qtbase/src/corelib/tools/qhash.h:607:32:   required from ‘QHashPrivate::Data<Node>::iterator QHashPrivate::Data<Node>::find(const Key&) const [with Node = QHashPrivate::Node<Empty, int>; QHashPrivate::Data<Node>::iterator = QHashPrivate::iterator<QHashPrivate::Node<Empty, int> >; QHashPrivate::Data<Node>::Key = Empty]’
../../cmake-build/qtbase/include/QtCore/../../../../qt5/qtbase/src/corelib/tools/qhash.h:1138:14:   required from ‘QHash<Key, T>::const_iterator QHash<Key, T>::find(const Key&) const [with Key = Empty; T = int]’
../../cmake-build/qtbase/include/QtCore/../../../../qt5/qtbase/src/corelib/tools/qhash.h:831:28:   required from ‘QTypeTraits::compare_eq_result_container<QHash<Key, T>, U> QHash<Key, T>::operator==(const QHash<Key, T>&) const [with U = int; Key = Empty; T = int; QTypeTraits::compare_eq_result_container<QHash<Key, T>, U> = bool]’
../../cmake-build/qtbase/include/QtCore/../../../../qt5/qtbase/src/corelib/kernel/qmetatype.h:2219:46:   required from ‘static bool QtPrivate::QEqualityOperatorForType<T, <anonymous> >::equals(const QtPrivate::QMetaTypeInterface*, const void*, const void*) [with T = NoCmpKeyHash; bool <anonymous> = true]’
../../cmake-build/qtbase/include/QtCore/../../../../qt5/qtbase/src/corelib/kernel/qmetatype.h:2340:54:   required from ‘constexpr const QtPrivate::QMetaTypeInterface QtPrivate::QMetaTypeInterfaceWrapper<NoCmpKeyHash>::metaType’
../../cmake-build/qtbase/include/QtCore/../../../../qt5/qtbase/src/corelib/kernel/qmetatype.h:2415:12:   required from ‘constexpr const QtPrivate::QMetaTypeInterface* QtPrivate::qMetaTypeInterfaceForType() [with T = NoCmpKeyHash]’
../../cmake-build/qtbase/include/QtCore/../../../../qt5/qtbase/src/corelib/kernel/qmetatype.h:2476:61:   required from ‘int qRegisterNormalizedMetaType(const QByteArray&) [with T = NoCmpKeyHash]’
../untitled/main.cpp:146:1:   required from here
../../cmake-build/qtbase/include/QtCore/../../../../qt5/qtbase/src/corelib/tools/qhashfunctions.h:209:14: error: no match for ‘operator==’ (operand types are ‘const Empty’ and ‘const Empty’)
  209 |     return a == b;
      |            ~~^~~~