Typescript: "include" doesn't accept models

[ugurkodak]

sequelize: 6.5.0
typescript: 4.1.3

import { Model } from 'sequelize';

interface FirstAttributes {
    id: number,
    one: string
}

class First extends Model<FirstAttributes, FirstAttributes> implements FirstAttributes {
    id!: number;
    one!: string;
}

interface SecondAttributes {
    id: number,
    two: string
}

class Second extends Model<SecondAttributes, SecondAttributes> implements SecondAttributes {
    id!: number;
    two!: string;
}

First.belongsTo(Second);

First.findOne({
    include: [Second]
});

include: [Second] causes this typescript error:

error TS2769: No overload matches this call.
  Overload 1 of 2, '(this: ModelStatic<First>, options: NonNullFindOptions<FirstAttributes>): Promise<First>', gave the following error.
    Type 'typeof Second' is not assignable to type 'Includeable'.
      Type 'typeof Second' is not assignable to type 'typeof Model'.
        Types of construct signatures are incompatible.
          Type 'new (values?: SecondAttributes | undefined, options?: BuildOptions | undefined) => Second' is not assignable to type 'new <TModelAttributes extends {} = any, TCreationAttributes extends {} = TModelAttributes>(values?: TCreationAttributes | undefined, options?: BuildOptions | undefined) => Model<TModelAttributes, TCreationAttributes>'.
            Types of parameters 'values' and 'values' are incompatible.
              Type 'TCreationAttributes | undefined' is not assignable to type 'SecondAttributes | undefined'.
                Type 'TCreationAttributes' is not assignable to type 'SecondAttributes | undefined'.
                  Type '{}' is not assignable to type 'SecondAttributes'.
                    Type 'TCreationAttributes' is not assignable to type 'SecondAttributes'.
                      Type '{}' is missing the following properties from type 'SecondAttributes': id, two
  Overload 2 of 2, '(this: ModelStatic<First>, options?: FindOptions<FirstAttributes> | undefined): Promise<First | null>', gave the following error.
    Type 'typeof Second' is not assignable to type 'Includeable'.
      Type 'typeof Second' is not assignable to type 'typeof Model'.

30     include: [Second]

If I define an association in the First model I can get rid of this error but I have to write First.association.second instead of providing model which actually works if I ignore typescript.

class First extends Model<FirstAttributes, FirstAttributes> implements FirstAttributes{
    id!: number;
    one!: string;

    public static associations: {
        second: Association<First, Second>
    }
}

First.findOne({
    include: [First.associations.second]
});

First.findOne({
    include: [{
        association: First.associations.second
    }]
});

Am I missing something or is this working as intended?