VB6 cannot see interface with indexed property

Question

I've created a simple type library with an interface which has an indexed property in it:

[
  uuid(EAC3FABB-2A00-4A91-BF80-F0CE394A648F),
  dual,
  oleautomation
]
interface MyInterface1: IDispatch
{
  [propget, id(0x000000C9)]
  HRESULT _stdcall Property1([in] VARIANT Index, [out, retval] short* Value);
  [propput, id(0x000000C9)]
  HRESULT _stdcall Property1([in] VARIANT Index, [in] short Value);
};

As soon as I add indexed property into the interface it disappears from VB6 IDE. Why is that? Are there any MIDL attributes that I need to add to my idl file?