[DGD] function clash weirdness

[Shentino]

Something I find odd is that if you inherit three (or more?) objects,
they all have to have labels or you get a clash error.

Here's the code:

inherit LIB_USER;
inherit account API_ACCOUNT; /* my own account manager api */
inherit user API_USER;

/* ... */

static void create(int clone)
{
    if (clone) {
        ::create();  /* here I get an "ambiguous call to ::create" */
        account::create();
        user::create()
    }
}

But if I stop inheriting API_ACCOUNT, the error goes away.

What's going on?  Am I doing something stupid?