Это баг в GCC 11.2 или я что-то упустил?

#include <iostream>
using namespace std;

#pragma pack(1)
struct RGBA {
    union {
        uint32_t word;
        struct {
            uint8_t r;
            uint8_t g;
            uint8_t b;
            uint8_t a;
        } rgba;
};
};
#pragma pack()

const RGBA RGBA_WHITE = { .rgba = { 0xff, 0xff, 0xff, 0xff } };
const RGBA RGBA_RED   = { .rgba = { 0xff, 0x00, 0x00, 0xff } };
const RGBA RGBA_GREEN = { .rgba = { 0x00, 0xff, 0x00, 0xff } };
const RGBA RGBA_BLUE  = { .rgba = { 0x00, 0x00, 0xff, 0xff } };
const RGBA RGBA_BLACK = { .rgba = { 0x00, 0x00, 0x00, 0xff } };
const RGBA RGBA_GREY  = { .rgba = { 0x80, 0x80, 0x80, 0xff } };
const RGBA RGBA_NONE  = { .rgba = { 0x00, 0x00, 0x00, 0x00 } };

int main(){
    auto color = RGBA_WHITE;
    cout << color.word << endl;
    color = RGBA_RED;
    cout << color.word << endl;
    return 0;
}

source>:18:62: error: too many initializers for 'RGBA::<unnamed union>'
   18 | const RGBA RGBA_WHITE = { .rgba = { 0xff, 0xff, 0xff, 0xff } };
      |                                                              ^
<source>:19:62: error: too many initializers for 'RGBA::<unnamed union>'
   19 | const RGBA RGBA_RED   = { .rgba = { 0xff, 0x00, 0x00, 0xff } };
      |                                                              ^