Unreal header tool bug

Unreal header tool could not parse class member initializion with {}. For example:

UCLASS()
class X_GAME_API UTest : public UBlueprintFunctionLibrary
{
    GENERATED_BODY()

public:
    UFUNCTION( BlueprintCallable, Category = "Test" )
    static void Test();
};

template< typename T >
class Foo
{
    int a;
public:
    Foo( int _a )
        : a{_a} // Valid C++, error there
};

Where I can report a bug?