get_TopLevelContainer not same as documentation ?

Hi

My code contains:

void foo(CComQIPtr<IWebBrowser2, &IID_IWebBrowser2> &spFrame)
{...
VARIANT_BOOL varBool;
hr = spFrame->get_TopLevelContainer(&varBool);
....
}

According to documentation vrBool should get VARIANT_TRUE if it is a
top container. However, instead of VARIANT_TRUE which is -1 , i get
the value of 1.

Is it a known bug? or did i misunderstood something?

Thanks
Noa

.