dereferencing pointer to incomplete type

["jens j." <jan0sch gmx net>]

Hello,

while I was trying to write some recursive functions for my current application
I got stuck with the following problem.

I have a structure like this :

typedef struct AdressBookItem {
        ...
        GtkCTreeNode *tree_item;
        struct _AdressBookItem *parent;
        ...
} AdressBookItem;

But when I try something like this in my code :

void blabla (AdressBookItem *adr) {
        ...
        GtkCTreeNode *parent;

        ...
        parent = adr->parent->tree_item;         << THIS LINE
        ...
}

I get a compiler error "dereferencing pointer to incomplete type" for THIS LINE.
I read some FAQs and Tutorials but didn't find an answer.

So could anybody please give me an advice?

Thanks very much.

jens