constructing on the fly recursive structure with vector

I would like to know why the following code is wrong to the compiler :

struct foo {
    int a;
    vector<foo> b;
};

int main() {
    foo c = foo{1, vector<foo>{1, vector<foo>{1}}};
}

whereas it compiles with this one:

foo c = foo{1, vector<foo>{1}};

Is that because this kind of nested structure construction is not supported or I am doing it all wrong ?