Invalid set index on base 'Dictionary' with value of type 'float'

[crystal grove]

I have a save data singleton with the following variables

    "knight": {
        "current": true
    }
}
const STARTER_STATS = {
        
    "highscore": 0,
     "sword_damage": 0,
     "spear_damage": 0,
     "anvil_damage": 0,
     "fireball_damage": 0,
     "axe_damage": 0,
     "spiked_armor_damage": 0,

    "potions_drank": 0,
    "speed_potions_drank": 0,
    "strength_potions_drank": 0,
    "health_potions_drank": 0
}

var save_data: Dictionary = {
    "meta_upgrade_currency": 0,
    "meta_upgrades": {

    },
    "characters": STARTER_CHARACTERS,
    "stats": STARTER_STATS
}

var stats:
    get:
        return save_data['stats']
    set(value):
        save_data['stats'] = value

whenever I try to increment one of the stats, like this:
SaveData.stats['total_damage_dealt'] += damage

I get the following error:
Invalid set index 'total_damage_dealt' (on base: 'Dictionary') with value of type 'float'

Any ideas why I can't update that stat? I've tried without the custom getter and setter and I get the same error. I can't think of any reason why I shouldn't be able to update that value since it's already initialized.

I'm in v4.2.stable.official [46dc27791]

[wicked estuary]

try setting to 0.0 instead (when initializing the dictionary)

[crystal grove]

I tried that and I get the same error unfortunately

[wicked estuary]

oh, why is the dictionary a constant?

it should be a variable if you are changing the values

well, the error would be different

[crystal grove]

ohh that was the issue tysm!

[wicked estuary]

bad error then