ValidationError when on db.create with Mongoose.Schema.Types.Decimal in model

Versions:
mongoose@4.11.5 mongodb Server version: 3.4.7

Model:

var mongoose = require('mongoose'),
Schema = mongoose.Schema;

var CheckSchema = new Schema({
    providerName: String,
    number: String,
    date:  { type: Date },
    dateReceived: { type: Date },
    amount: Schema.Types.Decimal,  
    paymentType: String,
    comment: String,
    status: String,
    images: [Image],
    transactions: [Transaction],
    rejectedTransactions: [Transaction],
    payerName: String
});

server code:

Check.create(newCheck, function (err, check) {
   if (err) {
      return _response.handleError(req, res, err, _logType);
   }
   return _response.handleSuccess(req, res, 200, _logType, check);
});

Returns this error:

Check validation failed: amount: Cast to Decimal128 failed for value 
"123.98" at path "amount"
ValidationError

"amount" is coming from the client as a number. When I stringify "amount" it succussfully stores to the db as a Decimal128 type.

newCheck.amount = newCheck.amount.toString();

I do not want to do that everytime I create a new check. I have a large app that I want to change multiply values to Decimal128. Is there something I am missing in my setup?