Mongoose subdocuments in typescript missing Model methods

I'm using mongoose with typescript and today I stepped into some confusion with Model and Document.

Here is definition of my subdocument.

export interface IUserUnitResource {
    serialNumber: string;
    role: string;
    name?: string;
    alarms: IUserAlarmResource[];
}

export interface IUserUnitEntity extends IUserUnitResource, mongoose.Document {
    alarms: mongoose.Types.DocumentArray<IUserAlarmEntity>;
}

export const userUnitSchema = new mongoose.Schema(
    {
        serialNumber: { type: String, required: true, index: true },
        role: { type: String, default: 'user' },
        name: String,
        alarms: { type: [userAlarmSchema], default: [] },
    },
    { _id: false }
);

In mongoose documentation they say:

An instance of a model is called a document.

So I assumed that i can call ownerDocument method on that subdocument. But typescript gives me an error:

Property 'ownerDocument' does not exist on type 'IUserUnitEntity'.

But if i try to call that method using any i get desired document.

(uu as any).ownerDocument()

Do I have the typings wrong, or it's a bug?