Mongoose: Can't save nested object to nested model

I have the following schema set up:

var TradeSchema = new mongoose.Schema({
        channel: String,
        trade: {
            tradeid: Number,
            timestamp: Date,
            datetime: Date,
            marketid: Number,
            marketname: String,
            quantity: Number,
            price: Number,
            total: Number,
            type: String
        }
    });

var MarketSchema = new mongoose.Schema({
        name: { type: String, index: true },
        trades: [TradeSchema]
    });

The Trade schema doesn't actually need to have the "trade" property nested like that, but I am getting it from anAPI and for now I want to keep that exactly as I got it.

The problem is, when I take the raw JS object:

{
    channel: 'trade.5',
    trade: {
        tradeid: '86554823',
        timestamp: 1425569593,
        datetime: '2015-03-05 10:33:13 EDT',
        marketid: '5',
        marketname: 'FTC/BTC',
        quantity: '957.65001732',
        price: '0.00001210',
        total: '0.01158757',
        type: 'Sell'
    }
}

...and I save it...

market.trades.push(trade);
market.save(function(err){
    if (err) console.log('Error saving trade to market.');
});

...it seems to strip out the 'trade' key, and this is all that gets saved to the db:

{ channel: 'trade.5', _id: 54f9e3056e23df1ee3e60327 }

Am I missing a validation step, mass-assignment problem, etc?