gcc fails with function specialization

With the following code gcc fails:

template <typename X = int, typename T, typename InIt, typename ...R>
    inline void func(const T& t, InIt b, InIt e, R... p)   {}
template <typename X = int, typename T, typename Iterable, typename ...R>
    inline void func(const T& t, const Iterable& i, R... p) {}

template <typename T>
    struct S {};

template <typename X = int, typename T, typename InIt, typename ...R>
    inline void func(const S<T>& t, InIt b, InIt e, R... p)   {}
template <typename X = int, typename T, typename Iterable, typename ...R>
    inline void func(const S<T>& t, const Iterable& i, R... p) {}

int main() {
    func(42, "");
    func(S<int>(), "");
    func(S<int>(), "", 1); // error
}

with:

<source>: In function 'int main()':
<source>:16:25: error: call of overloaded 'func(S<int>, const char [1], int)' is ambiguous
     func(S<int>(), "", 1);
                         ^
<source>:16:25: note: candidates are:
<source>:4:17: note: void func(const T&, const Iterable&, R ...) [with X = int; T = S<int>; Iterable = char [1]; R = {int}]
     inline void func(const T& t, const Iterable& i, R... p) {}
                 ^
<source>:11:17: note: void func(const S<T>&, const Iterable&, R ...) [with X = int; T = int; Iterable = char [1]; R = {int}]
     inline void func(const S<T>& t, const Iterable& i, R... p) {}

Tested with gcc v4.8.1 and v9.1. Compiles with clang (v3 and v8), icc (v13 and v19), msvc (v19.14 and v19.20).
Is the code valid or is this a bug in gcc?