Re-registration of singleton types doesn't work

cpp:
qmlRegisterType<MyType1>("MyModule", 1, 0, "MyType");
qmlRegisterType<MyType2>("MyModule", 1, 0, "MyType");
runSomeQmlApplication();

qml:
MyType{ ... }

cpp:
qmlRegisterSingletonType<MySingleton1>("MyModule", 1, 0, "MySingleton", createMySingleton1);
qmlRegisterSingletonType<MySingleton2>("MyModule", 1, 0, "MySingleton", createMySingleton2);

qml:
MySingleton.callSomeMethod();