Custom model data in advancement datapack

Im working on an advancement datapack, but ive been stuck trying to give icons a custom model data for hours.
It all works fine, datapack is fine etc, but whatever i try to do just doesnt work
  "display": {
    "icon": {
      "id": "minecraft:gold_ingot",
      "minecraft:custom_model_data": 1,
      "count": 1
    },
    "title": "Wagoo",
    "description": "The 'clart' of your journey",
    "background": "minecraft:textures/gui/advancements/backgrounds/adventure.png",
    "show_toast": true,
    "announce_to_chat": false
  },```