Clang cannot use braced initialization for user-defined conversion

The code follows.

struct A {
  A() {}
};

struct B {
  B() {}
  explicit operator A() { return A{}; }
};

struct C {
  A a;
  C(B b) : a{b} {}
};

I have a struct A which is not aggregate constructible (because it has a constructor defined). The same goes for struct B. But it also has an explicit user-defined conversion operator to struct A. Now struct C's constructor takes a struct B, and uses it to construct struct A. As on cppreference, the conversion operator can participate in direct initialization, which I believe is the case for the member initialization of struct C. It passes on GCC 5.2 (C++11). But however it fails on Clang 3.6. I tried with C++11, C++14, and C++1z.

If I change a{b} to a(b), it passes on both Clang and GCC.

I wonder if it is a Clang bug or I misunderstood the standard?