Pomelo.entityframeworkcore.mysql: .Net Core2 EF MySQL having issue while changing foreign key column to nullable

I am working on an application where I am using .Net Core 2, EF Core and MySQL as database server via Code First approach.

I have 2 tables:

1. User
2. Employee

User table is the main table which contains the user information and Employee table is the child table which has a column ID_User as shown below:

 public class User : BaseEntity
    {
        public int ID_User { get; set; }
        public string Name { get; set; }
        public string UserName { get; set; }
        public string Password { get; set; }

        public virtual ICollection<Employee> Employees{get;set;}
    }



 public class Employee : Entity
    {
        public int ID_Employee { get; set; }
        public string Name { get; set; }

        public int ID_User { get; set; }

        public virtual User User { get; set; }
    }

Everythihg works perfectly when I use the above mapping and I have enaugh data in both the tables.

Now, I want to make the column ID_User in Employee table as nullable

To implement this change I made folloeing change to my model:

public class Employee : Entity
    {
        public int ID_Employee { get; set; }
        public string Name { get; set; }

        public int? ID_User { get; set; }

        public virtual User User { get; set; }
    }

and in mapping file:

builder.HasOne(x=>x.User).WithMany(y=>y.Employees).HasForeignKey(z=>z.ID_User).IsRequired(false);

After running the dotnet ef migrations add empuser command it generated the following migration code:

migrationBuilder.DropForeignKey(
name: "FK_Employee_User_ID_User",
table: "Employee");

    migrationBuilder.AlterColumn<int>(
        name: "ID_User",
        table: "Employee",
        nullable: true,
        oldClrType: typeof(int));

    migrationBuilder.AddForeignKey(
        name: "FK_Employee_User_ID_User",
        table: "Employee",
        column: "ID_User",
        principalTable: "User",
        principalColumn: "ID_User",
        onDelete: ReferentialAction.Restrict);

Now when I run dotnet ef database update it is giving me the following error:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CONSTRAINT FK_Employee_User_ID_User' at line 1

Please help.

Thanks