Make Mongoose property no longer unique - node.js

Question

Im getting a bizarre error with Mongoose. When a user registers they give the name of the organisation they belong to. Previously, this needed to be unique. My schema was:
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var Organisation = new mongoose.Schema({
name: {
type: String,
required: true,
unique: true
},
createdById: {
type: Schema.Types.ObjectId,
ref: 'User'
},
createdOn: {
type: Date,
"default": Date.now
},
availableUntil: {
type: Date
}
});
Organisation.path('name').validate(function(value, done) {
var self = this;
if (!self.isNew) {
return done(true);
} else {
//mongoose.models['Organisation'] or self.model('Organisation')
mongoose.models['Organisation'].count({
name: value
}, function(err, count) {
if (err) {
return done(err);
}
return done(!count)
});
}
}, "This email already exists");
mongoose.model('Organisation', Organisation);
But now it doesn't matter, an organisation name doesn't need to be unique. So I changed to:
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var Organisation = new mongoose.Schema({
name: {
type: String,
required: true
},
createdById: {
type: Schema.Types.ObjectId,
ref: 'User'
},
createdOn: {
type: Date,
"default": Date.now
},
availableUntil: {
type: Date
}
});
mongoose.model('Organisation', Organisation);
Note how unique: true has been removed.
I've restarted the server but bizarrely, I still get the error:
name: 'MongoError',
message: 'E11000 duplicate key error index: redmatter.organisations.$name_1 dup key: { : "delete me" }',
driver: true,
code: 11000,
index: 0,
errmsg: 'E11000 duplicate key error index: redmatter.organisations.$name_1 dup key: { : "delete me" }',
getOperation: [Function],
toJSON: [Function],
toString: [Function] }
How is this possible? Why am I getting a duplicate key error when I don't care if the name is not unique?