Compiler Bug? Can't use IStream* in interface before using [satyp

[ClockWinder]

I am defining a COM IDispatch interface.
The following causes a compiler error:

[id(3), helpstring("met hod Meth1")] HRESULT Meth1([in] IStream* data);
[id(4), helpstring("met hod Meth2")] HRESULT Meth2([out,retval,saty pe("BSTR")] SAFEARRAY** list);

error C2440: 'initializing' : cannot convert from 'VARIANT' to 'IStream *'

Whereas removing the satype attribute or switching the id values does not.