PGraphics saves fully transparent instead of red (P2D)

Created by: clankill3r

Processing 4.2, OSX 10.15.7

void setup() {
  size(600, 600, P2D);
  PGraphics pg = createGraphics(64, 64, P2D);
  pg.beginDraw();
  pg.background(255, 0, 0);
  pg.endDraw();

  image(pg, 0, 0);

  pg.save("bug.png");
}

It should save a red image, but it's fully transparent.