C++11 default class member initialization with initializer list , simultaneously

Can someone point me please, to a corresponding paragraph of the C++ standard, or maybe can provide some explanation why my code does not compile if I uncomment the text ({123})?

Generally speaking I understand what something wrong with usage of default member initialization and initialization via initializer list, but I can't refer to exact reasons.

enum class MY: int
{
    A = 1
};

struct abc
{
    int a;/*{123};*/  //compilation failed if uncommented
    MY m;
};

abc a = {1, MY::A};

Compiler error, in case of uncommented text:

error: could not convert ‘{1, A}’ from ‘<brace-enclosed initializer list>’ to ‘abc’